Name: separation of aldehydes and reactive ketones from mixtures using a bisulfite extraction protocol
Uploaded: 2018-04-02T15:00:00.000+00:00
Duration: 9 min 8 s
Description: Watch this Scientific Journal Video about Separation of Aldehydes and Reactive Ketones from Mixtures Using a Bisulfite Extraction Protocol at JoVE.com

Bildirim Amerikan Kimya Derneği petrol araştırma fonu Bu araştırmanın kısmi destek için bağış için yapılır. Bu araştırma desteklenen yenileme ve enstrümantasyon hibeler için Ulusal Bilim Vakfı (CHE-0619275 ve CHE-0963165) için sana şükrediyoruz.

1. standart protokolü için aromatik aldehitler ayrılması bir karışımı. Örnek: Benzil bütrat ayrılması üzerinden Anisaldehyde ile 1:1 karışımı.
<ol><li>Anisaldehyde 175 μL ve Benzil bütrat metanol 5 ml 250 μL dağıtılması ve çözüm için HCI'yi bir huni aktarmak. Dikkat: Sodyum bisülfit kükürt dioksit gaz oluşturabilir, böylece bu protokole uygun havalandırma ile gibi bir duman mahallede yapılmalıdır.</li>
	<li>1 mL doymuş sulu Sodyum bisülfit ekleyin ve şiddetle çalkalanır için yaklaşık 30 s.</li>
	<li>25 mL deiyonize su ve % 10 Etil asetat/hexanes 25 mL ekleyin ve şiddetle çalkalanır.</li>
	<li>Katmanları ayrı. Susuz Magnezyum sülfat ile organik katman kuru. Magnezyum sülfat kaldırmak ve bir döner Buharlaştırıcı kullanma olarak vacuo konsantre çözüm filtre.</li>
</ol>2. ayrılık Alifatik aldehitler ve ketonlar bir karışımı. Örnek: Benzil bütrat ayrılması üzerinden Benzylacetone ile 1:1 karışımı.
<ol><li>Benzylacetone 213 μL ve Benzil bütrat dimethylformamide 10 ml 250 μL dağıtılması ve çözüm için HCI'yi bir huni aktarmak. Dikkat: Sodyum bisülfit kükürt dioksit gaz oluşturabilir, böylece bu protokole uygun havalandırma ile gibi bir duman mahallede yapılmalıdır.</li>
	<li>25 mL doymuş sulu Sodyum bisülfit ekleyin ve şiddetle çalkalanır için yaklaşık 30 s.</li>
	<li>25 mL deiyonize su ve % 10 Etil asetat/hexanes 25 mL ekleyin ve şiddetle çalkalanır.</li>
	<li>Katmanları ayrı. Sulu katman HCI'yi huni dönmek, 25 mL % 10 Etil asetat/hexanes ekleyin ve şiddetle çalkalanır. Sulu katmanı organik katman HCI'yi hunide bırakarak, drenaj. Geri HCI'yi huni önceki organik katmanı ekleyin.</li>
	<li>Kombine organik katmanları üç kez deiyonize su (her yıkama için 10 mL) ile yıkayın. Susuz Magnezyum sülfat ile organik katman kuru. Magnezyum sülfat kaldırmak ve bir döner Buharlaştırıcı kullanma olarak vacuo konsantre çözüm filtre.</li>
</ol>3. aldehitler ayrılması üzerinden bir Alkene içeren bir karışımı. Örnek: Benzil bütrat ayrılması üzerinden Citronellal ile 1:1 karışımı.
<ol><li>Citronellal 255 μL ve Benzil bütrat dimethylformamide 10 ml 250 μL dağıtılması ve çözüm için HCI'yi bir huni aktarmak. Dikkat: Sodyum bisülfit kükürt dioksit gaz oluşturabilir, böylece bu protokole uygun havalandırma ile gibi bir duman mahallede yapılmalıdır.</li>
	<li>25 mL doymuş sulu Sodyum bisülfit ekleyin ve şiddetle çalkalanır için yaklaşık 30 s.</li>
	<li>25 mL deiyonize su ve hexanes 25 mL ekleyin ve şiddetle çalkalanır.</li>
	<li>Katmanları ayrı. Sulu katman HCI'yi huni dönmek, 25 mL hexanes eklemek ve şiddetle çalkalanır. Sulu katmanı organik katman HCI'yi hunide bırakarak, drenaj. Geri HCI'yi huni önceki organik katmanı ekleyin.</li>
	<li>Kombine organik katmanları üç kez deiyonize su (her yıkama için 10 mL) ile yıkayın. Susuz Magnezyum sülfat ile organik katman kuru. Magnezyum sülfat kaldırmak ve bir döner Buharlaştırıcı kullanma olarak vacuo konsantre çözüm filtre.</li>
</ol>4. aldehitler bir karışımı üzerinden yeniden yalıtım. Örnek: Piperonal ayrılması üzerinden Benzil bütrat ile 1:1 karışımı.
<ol><li>217 mg piperonal ve Benzil bütrat metanol 5 ml 250 μL dağıtılması ve çözüm için HCI'yi bir huni aktarmak. Dikkat: Sodyum bisülfit kükürt dioksit gaz oluşturabilir, böylece, bu protokole uygun havalandırma ile gibi bir duman mahallede yapılmalıdır.</li>
	<li>1 mL doymuş sulu Sodyum bisülfit ekleyin ve şiddetle çalkalanır için yaklaşık 30 s.</li>
	<li>25 mL deiyonize su ve % 10 Etil asetat/hexanes 25 mL ekleyin ve şiddetle çalkalanır.</li>
	<li>Katmanları ayrı. Sulu katman HCI'yi huni geri dönün.<ol>
<li>İsteğe bağlı: sulu katmanla bir kez % 10 Etil asetat/hexanes kalan Benzil bütrat az miktarda kaldırmak için 25 mL yıkayın.</li>
	</ol>
</li>
	<li>25 mL Etil asetat ekleyin ve bir pH şerit pH 12 olduğunu gösterir kadar % 50 sodyum hidroksit ekleyin. Şiddetle çalkalanır. Dikkat: Gaz evrim bu adımı sırasında gözlenen ve basınç birikmesi neden olabilir. Düzgün HCI'yi huni havalandırma emin olun. Bu yordamı ölçekleme gaz evrim daha belirgin hale getirir. Dikkatli olun.</li>
	<li>Katmanları ayrı. Sulu katman HCI'yi huni dönün ve Etil asetat 25 mL ekleyin. Şiddetle çalkalanır.</li>
	<li>Katmanları ayrı. Önceki adımdaki organik katmanı organik katmanla birleştirin. Susuz Magnezyum sülfat ile kombine organik katman kuru. Magnezyum sülfat kaldırmak ve bir döner Buharlaştırıcı kullanma olarak vacuo konsantre çözüm filtre.</li>
</ol>

<ol>
	<li>Boucher, M. M., Furigay, M. H., Quach, P. K., Brindle, C. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Liquid-Liquid+Extraction+Protocol+for+the+Removal+of+Aldehydes+and+Highly+Reactive+Ketones+from+Mixtures.">Liquid-Liquid Extraction Protocol for the Removal of Aldehydes and Highly Reactive Ketones from Mixtures.</a> Org. Process Res. Dev. 21 (9), 1394-1403 (2017).</li><li>Lauer, G. G., Pratt, R. S., Wilson, W. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Separation+of+Aldehydes+and+Ketones.">Separation of Aldehydes and Ketones.</a> , (1951).</li><li>Hsu, W. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Separation of Aldehydes from Ketones via Acid-Catalyzed Cyclotrimerization of the Aldehyde. , 4701561 (1987).</li><li>Schreiber, R. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Process+for+Separating+Aldehydes+and+Ketones.">Process for Separating Aldehydes and Ketones.</a> , (1942).</li><li>Bludworth, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Separation+of+Aldehyde-Ketone+Mixtures.">Separation of Aldehyde-Ketone Mixtures.</a> , (1944).</li><li>Masilamani, D., Manahan, E. H., Vitrone, J., Rogic, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Organic+Reactions+of+Sulfur+Dioxide.+Reactions+with+Nucleophilic+Double+Bonds+Leading+to+the+Isomerization,+Aromatization,+Selective+Hydrogen-Deuterium+Exchange,+and+Electron-Transfer+Proceses.">Organic Reactions of Sulfur Dioxide. Reactions with Nucleophilic Double Bonds Leading to the Isomerization, Aromatization, Selective Hydrogen-Deuterium Exchange, and Electron-Transfer Proceses.</a> J. Org. Chem. 48 (25), 4918-4931 (1983).</li><li>Masilamani, D., Rogic, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Organic+Reactions+of+Sulfur+Dioxide.+4.+A+Facile+Regiospecific+Hydrogen-Deuterium+Exchange+in+Olefins.+Consequence+of+the+Intermediacy+of+Allylic+Sulfinic+Acids+in+the+Ene+Reaction+of+Sulfur+Dioxide+with+Double+Bonds.">Organic Reactions of Sulfur Dioxide. 4. A Facile Regiospecific Hydrogen-Deuterium Exchange in Olefins. Consequence of the Intermediacy of Allylic Sulfinic Acids in the Ene Reaction of Sulfur Dioxide with Double Bonds.</a> J. Am. Chem. Soc. 100 (14), 4634-4635 (1978).</li><li>Makitra, R. G., Kal'muk, S. D., Bryk, D. V., Polyuzhin, I. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Factors+Controlling+Sulfur+Dioxide+Solubilities+in+Organic+Solvents.">Factors Controlling Sulfur Dioxide Solubilities in Organic Solvents.</a> Russ. J. Inorg. Chem. 55 (8), 1322-1329 (2010).</li><li>van Dam, M. H. H., Lamine, A. S., Roizard, D., Lochon, P., Roizard, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selective+Sulfur+Dioxide+Removal+Using+Organic+Solvents.">Selective Sulfur Dioxide Removal Using Organic Solvents.</a> Ind. Eng. Chem. Res. 36 (11), 4628-4637 (1997).</li><li>Li, H., Jiao, X., Chen, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solubility+of+Sulphur+Dioxide+in+Polar+Organic+Solvents.">Solubility of Sulphur Dioxide in Polar Organic Solvents.</a> Phys. Chem. Liq. 52 (2), 349-353 (2014).</li><li>Trost, B. M., Brindle, C. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Direct+Catalytic+Asymmetric+Aldol+Reaction.">The Direct Catalytic Asymmetric Aldol Reaction.</a> Chem. Soc. Rev. 39 (5), 1600 (2010).</li></ol>

Yazarlar ifşa gerek yok.

Bisülfit tepki tipik bir iki aşamalı çıkarma kullanarak aldehitler kaldırmak için bir yöntem olarak kullanmak için ilk girişimleri kaldırma çok az düzeyde yol açtı. Biz tepki iki kat temas halinde olduğunu çok sınırlı süre içinde gerçekleşmesi için yeterince hızlı değildi onaylanmadığına karar. Reaktanları arasında temas artırmak için hangi su karışan bir çözücü başlangıçta yeterli immiscible bir çözücü getirilmesi önce Reaktanları karıştırma sağlamak için kullanıla...

Karışımlar bileşenlerinin ayrılması başka bir saf malzemelerin hazırlanması esastır. Yöntem tanımlamak burada aldehitler facile ayırma için verir ve sterically döngüsel engelsiz ve metil ketonlar diğer organik moleküllerin1. Bisülfit bir şarj oluşturmak için karbonil grubu ile reaktivite teknik dayanan bu adduct diğer bileşenleri bir immiscible organik katmana ayrı iken sulu bir katmana, ayrılabilir. Reaktivite Bisülfit ve karbonil arasında ulaşmanın anahtarı ayrılık ayrı bölüm içine önce gerçekleşmesi tepki verir karışan bir çözücü kullanımıdır. Karışan çözücü en az mesafeyi ilavesi, muhtemelen Bisülfit hidrofilik ve hidrofobik organik arasında fakir temas nedeniyle elde edilir.
Bu ayırma yöntem arıtma için protokol kolaylığı avantajdır. Sıvı-sıvı ekstraksiyon gerçekleştirmek için basit bir işlem olduğunu ve büyük ölçüde yapılabilir. Sütun Kromatografi gibi alternatif arıtma teknikleri çok daha pahalı, zaman alıcı ve zor bileşenleri polarite açısından yeterli farklılaşma gerektirir ve büyük ölçekte gerçekleştirmek için vardır. Rekristalizasyon veya damıtma arındırıcı çözünürlük veya bileşenlerinden biri karışım kaynama noktaları arasında yeterli farklılaşma sırasıyla gerektirir. Bisülfit ayıklama reaktivite aldehitler ve ketonlar karbonil grubunun farklılığı kullandığından, bileşikler benzer çözünürlük, kaynama noktası veya polarizasyona ile etkili bir şekilde ayrılabilir. Diğer kimyasal ayırma yöntemleri seçici ayrılması aldehitler ve ketonlar için karışımları, örneğin, oximes2, çevrimsel acetals3veya mercaptal4 oluşumu seçici oluşumu adlı biri yok. Bu yöntemler ürün suda çözünür değildir ve bu nedenle basit ayıklama protokolü tarafından ayrı olamaz çünkü kurulan bu tür karışım, ayırmak için ek bir adım gerektirir. Aldehid oksidasyon çıkarılabilir karboksilik asitler oluşturmak için başka bir tekniği5bildirdi ancak gerekli oksidasyon adım daha az chemoselective daha hafif Bisülfit koşullar burada açıklanan ve oksijen gazı kullanımı ve kobalt katalizör gerekir olduğunu.
Bu yöntem bu fonksiyonel gruplar içermeyen molekülleri aldehitler (şekil 1) ve sterically engelsiz döngüsel ve metil keton (Şekil 2) ayrılması için geçerlidir. α-keto esterleri gibi özellikle reaktif ketonlar de bu işlemiyle kaldırılır. Alkanes, alkenes, hava dienes, alkynes, esterler, amidler, karboksilik asitler, alkil halojenürlerden, alkoller, fenoller, Nitriller, Benzil klorür, epoksitler, ornatıklanmış, acetals, ve biraz engel, α, β-doymamış, veya aril ketonlar koşullar altında tüm tepkisizdir ve aldehit veya reaktif keton bileşeni karışımı (rakamlar 2 ve şekil 3) ayrılabilir. Etil keton veya döngüsel ketonlar, α-yerine Örneğin, yeterince engel ve bu nedenle aldehitler ve ketonlar daha reaktif ayrılabilir. Alkenes kullanırken, hekzan kükürt dioksit Bisülfit çözümde mevcut nedeniyle istenmeyen ayrışma önlemek için immiscible solvent önerilir. Fonksiyonel grup uyumluluk Bisülfit ayıklama Protokolü'nün son derece geniştir ve bu nedenle bir aldehit veya Engelsiz bir karışım ayrı kalmak karbonil geçen madde olması durumunda ayrımları, son derece geniş bir yelpazesi için geçerlidir metil veya döngüsel keton. Daha az reaktif keton Bisülfit bu koşullarda ile tepki yok ve bu nedenle kaldırılmadı.

<table><tbody><tr><td>sodium bisulfite</td><td>Fisher</td><td>AC419440010&amp;nbsp;</td><td>1 kg</td></tr><tr><td>benzyl butyrate</td><td>Fisher</td><td>AAB2424130&amp;nbsp;</td><td>250 g</td></tr><tr><td>anisaldehyde</td><td>Fisher</td><td>AC104801000&amp;nbsp;</td><td>100 mL</td></tr><tr><td>magnesium sulfate</td><td>Fisher</td><td>M65-500&amp;nbsp;</td><td>500 g</td></tr><tr><td>ethyl acetate</td><td>Fisher</td><td>E195-4&amp;nbsp;</td><td>4 L</td></tr><tr><td>hexanes</td><td>Fisher</td><td>H292-4&amp;nbsp;</td><td>4 L</td></tr><tr><td>methanol&amp;nbsp;</td><td>Fisher</td><td>A456-1&amp;nbsp;</td><td>1 L</td></tr><tr><td>dimethylformamide</td><td>Fisher</td><td>D119-1&amp;nbsp;</td><td>1 L</td></tr><tr><td>citronellal</td><td>Fisher</td><td>AAL15753AE&amp;nbsp;</td><td>100 mL</td></tr><tr><td>benzylacetone&amp;nbsp;</td><td>Fisher</td><td>AC105832500&amp;nbsp;</td><td>250 mL</td></tr><tr><td>deionized water</td><td>Fisher</td><td>BP28194&amp;nbsp;</td><td>4 L</td></tr><tr><td>piperonal&amp;nbsp;</td><td>Sigma-Aldrich</td><td>P49104-25G</td><td>25 G</td></tr><tr><td>sodium hydroxide</td><td>Fisher</td><td>S318-1&amp;nbsp;</td><td>1 kg</td></tr><tr><td>separatory funnel with cap</td><td>Fisher</td><td>10-437-5B&amp;nbsp;</td><td>125 mL</td></tr><tr><td>ring stand</td><td>Fisher</td><td>03-422-215</td><td>3 aluminum rods</td></tr><tr><td>ring clamp</td><td>Fisher</td><td>12-000-104&amp;nbsp;</td><td>5 cm</td></tr><tr><td>cork ring</td><td>Fisher</td><td>07-835AA&amp;nbsp;</td><td>8 cm outer dimension</td></tr><tr><td>round bottom flask</td><td>Fisher</td><td>31-501-107&amp;nbsp;</td><td>100 mL</td></tr><tr><td>rotary evaporator with accessories</td><td>Fisher</td><td>05-000-461&amp;nbsp;</td><td>cold trap bondenser</td></tr><tr><td>bump trap 14/20 joint</td><td>Fisher</td><td>CG132201</td><td>14/20 joint</td></tr><tr><td>funnel</td><td>Fisher</td><td>05-555-6&amp;nbsp;</td><td>organic solvent compatible</td></tr><tr><td>cotton</td><td>Fisher</td><td>22-456-881</td><td>non-sterile</td></tr><tr><td>glass pipets</td><td>Fisher</td><td>13-678-20A&amp;nbsp;</td><td>borosilicate 5.75&quot;</td></tr><tr><td>two 250 microliter syringes</td><td>Fisher</td><td>14-813-69&amp;nbsp;</td><td></td></tr><tr><td>4 erlenmeyer flasks</td><td>Fisher</td><td>10-040D&amp;nbsp;</td><td>125 mL</td></tr><tr><td>fume hood&amp;nbsp;</td><td>Fisher</td><td>13-118-370&amp;nbsp;</td><td></td></tr><tr><td>nitrile gloves</td><td>Fisher</td><td>19-149-863B&amp;nbsp;</td><td>medium</td></tr><tr><td>safety goggles</td><td>Fisher</td><td>17-377-403&amp;nbsp;</td><td></td></tr><tr><td>spatula</td><td>Fisher</td><td>14-357Q</td><td></td></tr><tr><td>balance</td><td>Fisher</td><td>01-912-403&amp;nbsp;</td><td>120 g capacity</td></tr></tbody></table>

separation of aldehydes and reactive ketones from mixtures using a bisulfite extraction protocol

Organik bileşiklerin saflaştırılması rutin sentetik işlemleri temel bir bileşenidir. Şarj edilmiş bir yapı oluşturarak sulu bir katmana kirletici kaldırmak için ayıklama basit arıtma tekniği kullanmak için bir fırsat sağlar. Doymuş Sodyum bisülfit, aldehitler ve ketonlar reaktif karışan organik çözücü kullanımı başarılı bir şekilde içine dönüştürülmüş birleştirme tarafından tahsil Bisülfit adducts olabilir sonra bir karışımı diğer organik bileşenlerden ayrılması bir immiscible organik katmanı getirilmesi. Burada, aldehitler, sterically engel neopentyl aldehitler ve kimyasal karışımlar gelen bazı ketonlar da dahil olmak üzere kaldırılması için basit bir protokol açıklayın. Ketonlar sterically döngüsel engelsiz Eğer ayrılabilir ya da metil keton. Alifatik aldehitler ve ketonlar, dimethylformamide karışan solvent kaldırma oranlarını artırmak için kullanılır. Bisülfit ek tepki basification için bir karışım reaktif karbonil bileşeni izolasyon yeniden sağlar sulu tabakasının ters kaydedilebilir.

Yordam 1 aldehid kaldırılmak için aromatik aldehitler kullanılır. Yordam 2dimethylformamide karışan solvent kullanıldığı, Alifatik aldehitler ve ketonlar için kullanılmalıdır. Yordam 2 tam olarak metanol içinde çözünür değildir karışımları için kullanılmalıdır. Her iletişim kuralları elde edilen malzeme kitle tarafından 1H NMR Tümleştirme analiz kullanarak saflık ve kurtarma oranı için anali...

Watch this Scientific Journal Video about Separation of Aldehydes and Reactive Ketones from Mixtures Using a Bisulfite Extraction Protocol at JoVE.com

Separation of Aldehydes and Reactive Ketones from Mixtures Using a Bisulfite Extraction Protocol

Aldehitler ve ketonlar reaktif ayrılması Bisülfit ayıklama protokolü kullanılarak karışımları

Burada, aldehitler ve ketonlar reaktif karışımları sıvı-sıvı ekstraksiyon doymuş Sodyum bisülfit karışan bir çözücü içinde doğrudan protokolüyle kaldırmak için bir protokol mevcut. Bu kombine hızlı ve facile gerçekleştirmek için iletişim kuralıdır. Aldehit veya keton sulu katman basification tarafından yeniden izole.

The purification of organic compounds is an essential component of routine synthetic operations. The ability to remove contaminants into an aqueous layer ...

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33.8K Görüntüleme.  Trinity College. Burada, aldehitler ve ketonlar reaktif karışımları sıvı-sıvı ekstraksiyon doymuş Sodyum bisülfit karışan bir çözücü içinde doğrudan protokolüyle kaldırmak için bir protokol mevcut. Bu kombine hızlı ve facile gerçekleştirmek için iletişim kuralıdır. Aldehit veya keton sulu katman basification tarafından yeniden izole.

Video: Separation of Aldehydes and Reactive Ketones from Mixtures Using a Bisulfite Extraction Protocol

Synthesis of Esters Via a Greener Steglich Esterification in Acetonitrile

The Steglich esterification is a widely-used reaction for the synthesis of esters from carboxylic acids and alcohols. While efficient and mild, the reaction is commonly performed using chlorinated or amide solvent systems, which are hazardous to human health and the environment. Our methodology utilizes acetonitrile as a greener and less hazardous solvent system. This protocol exhibits rates and yields that are comparable to traditional solvent systems and employs an extraction and wash sequence that eliminates the need for the purification of the ester product via column chromatography. This general method can be used to couple a variety of carboxylic acids with 1&#176; and 2&#176; aliphatic alcohols, benzylic and allylic alcohols, and phenols to obtain pure esters in high yields. The goal of the protocol detailed here is to provide a greener alternative to a common esterification reaction, which could serve useful for ester synthesis in both academic and industrial applications.

A modified Steglich esterification reaction was used to synthesize a small library of ester derivatives with primary and secondary alcohols. The methodology uses a non-halogenated and greener solvent, acetonitrile, and enables product isolation in high yields without the need for chromatographic purification.

Esterleri bir yeşil Steglich esterleşme Asetonitril içinde yolu ile sentezi

The Steglich esterification is a widely-used reaction for the synthesis of esters from carboxylic acids and alcohols. While efficient and mild, the ...

Kimya

Preparation of Contiguous Bisaziridines for Regioselective Ring-Opening Reactions

Aziridines, a class of reactive organic molecules containing a three-membered ring, are important synthons for the synthesis of a large variety of functionalized nitrogen-containing target compounds through the regiocontrolled ring-opening of C-substituted aziridines. Despite the tremendous progress in aziridine synthesis over the past decade, accessing contiguous bisaziridines efficiently remains difficult. Therefore, we were interested in synthesizing contiguous bisaziridines bearing an electronically diverse set of N-substituents beyond the single aziridine backbone for regioselective ring-opening reactions with diverse nucleophiles. In this study, chiral contiguous bisaziridines were prepared by organocatalytic asymmetric aziridination of chiral (E)-3-((S)-1-((R)-1-phenylethyl)aziridin-2-yl)acrylaldehyde with N-Ts-O-tosyl or N-Boc-O-tosyl hydroxylamine as the nitrogen source in the presence of (2S)-[diphenyl(trimethylsilyloxy)methyl]pyrrolidine as a chiral organocatalyst. Also demonstrated here are representative examples of regioselective ring-opening reactions of contiguous bisaziridines with a variety of nucleophiles such as sulfur, nitrogen, carbon, and oxygen, and the application of contiguous bisaziridines to the synthesis of multi-substituted chiral pyrrolidines by Pd-catalyzed hydrogenation.

Contiguous bisaziridines containing non-activated and activated aziridines were synthesized by asymmetric organocatalytic aziridinations and then subjected to chemoselective ring-opening reactions under acidic or basic conditions. The non-activated aziridine ring opens with less reactive nucleophiles under acidic conditions, whereas the activated aziridine ring opens with more reactive nucleophiles under basic conditions.

Regioselektif halka açma reaksiyonları için bitişik bisaziridinlerin hazırlanması

Aziridines, a class of reactive organic molecules containing a three-membered ring, are important synthons for the synthesis of a large variety of ...

Reducing Agents

Source: Vy M. Dong and Daniel Kim, Department of Chemistry, University of California, Irvine, CA
Controlling the reactivity and selectivity during the synthesis of a molecule is very important criteria for chemists. This has led to the development of many reagents that allow chemists to pick and choose reagents suitable for a given task. Quite often, a balance between reactivity and selectivity needs to be achieved. This experiment will use IR spectroscopy to monitor the reaction and to understand the reactivity of carbonyl compounds as well as the reactivity of hydride-reducing reagents.

Reduction of Carbonyl Compounds

Source: Vy M. Dong and Daniel Kim, Department of Chemistry, University of California, Irvine, CA
Controlling the reactivity and selectivity during the ...

JoVE Science Education

Organik Kimya II

Alcohols from Carbonyl Compounds: Reduction

Reduction is a simple strategy to convert a carbonyl group to a hydroxyl group. The three major pathways to reduce carbonyls to alcohols are catalytic hydrogenation, hydride reduction, and borane reduction.
Catalytic hydrogenation is similar to the reduction of an alkene or alkyne by adding H2 across the pi bond in the presence of transition metal catalysts like Raney Ni, Pd&#8211;C, Pt, or Ru. Aldehydes and ketones can be reduced by this method, often under mild to moderate heat (25&#8211;100&#176;C) and pressure (1&#8211;5 atm H2), to yield 1&#176; and 2&#176; alcohols, respectively.
<img alt="Figure1" src="/files/ftp_upload/11925/11925_PT_Figure_1.svg" style="text-align: center; height: 90px;" />
Figure 1. Catalytic hydrogenation can be suitable for industrial applications when harsh conditions are not required, but unsaturated carbon&#8211;carbon bonds are also reduced.
Hydride reduction can be achieved by hydride transfer reagents, like sodium borohydride (NaBH4) and lithium aluminum hydride (LiAlH4, or LAH), as nucleophilic attack by a free hydride ion, <img alt="Figure2" src="/files/ftp_upload/11925/11925_PT_Figure_2.svg" style="height: 18px;" />, is almost unknown for NaH salts due to its high charge density, making it a strong base. The hydrogen atoms of LAH and NaBH4, being covalently bonded to boron and aluminum atoms, have partial negative charges, thereby enhancing their nucleophilicity at the cost of basicity. The first step of nucleophilic addition leads to the formation of alkoxide ions. The byproduct alkoxyborohydride or alkoxyaluminate reduces three more carbonyl molecules, successively transferring all their hydrogen atoms. Since hydride is a poor leaving group, the hydride transfer steps are irreversible, and therefore the reaction proceeds to completion. Lastly, the reaction mixture is worked up with solvent (i.e., water or alcohol in the case of NaBH4 and dilute acid in the case of LAH).
<img alt="Figure3" src="/files/ftp_upload/11925/11925_PT_Figure_3.svg" style="text-align: center; height:55px;" />
Figure 2. Aldehydes and symmetrical esters produce one 1&#176; alcohol product. Unsymmetrical esters produce a mixture of 1&#176; alcohols.
LAH, NaBH4, and their derivatives are highly useful in the reduction of aldehydes and ketones. LAH, a powerful reducing agent, can also reduce carbonyl compounds like acids, esters, acyl chlorides, and amides. LAH reacts violently with water and other protic solvents, liberating hydrogen gas and forming metal hydroxides/alkoxides. Hence, LAH reductions are typically carried out in aprotic solvents like anhydrous diethyl ether and THF.
<img alt="Figure4" src="/files/ftp_upload/11925/11925_PT_Figure_4.svg" style="text-align: center; height: 45px;" />
Figure 3. An alcoholic solution of lithium borohydride is a non-hazardous alternative to LAH in selectively reducing esters over acids.
On the other hand, NaBH4 is of a milder nature and generally reduces only in protic solvents like ethanol or methanol. Therefore, NaBH4 can be used to reduce aldehydes and ketones in the presence of functional groups like alkyl halides, esters, alkyl tosylates, and nitro groups. Diisobutylaluminum hydride (DIBAL-H) can also convert carbonyls to alcohols at room temperature by two successive additions of hydride ions. However, when reacted with esters at low temperatures, this reaction can be stopped at the aldehyde stage by adding only one equivalent of hydride ion.
Borane reduction uses a borane (BH3) solution in diethyl ether, THF, or Me2S to selectively reduce electron-rich carbonyl groups like carboxylic acids in the presence of other reducible functional groups such as esters and even ketones.
<img alt="Figure5" src="/files/ftp_upload/11925/11925_PT_Figure_5.svg" style="text-align: center; height: 65px;" />
Figure 4. The formation of a reactive triacylborate intermediate with a more electrophilic carbonyl group than the starting ester molecule drives the reduction reaction forward.
For living organisms, reduced coenzyme NADH or its phosphoester NADPH is equivalent to laboratory hydride reagents in enzyme catalysis of similar biological reductions.

Karbonil Bileşiklerinden Elde Edilen Alkoller: İndirgeme

Reduction is a simple strategy to convert a carbonyl group to a hydroxyl group. The three major pathways to reduce carbonyls to alcohols are catalytic ...

Organik Kimya

Unit 1

Alkoller ve Fenoller

KEY TERMS AND CONCEPTS

Preparation of Aldehydes and Ketones from Alcohols, Alkenes, and Alkynes

Aldehydes and ketones are prepared from alcohols, alkenes, and alkynes via different reaction pathways. Alcohols are the most commonly used substrates for synthesizing aldehydes and ketones. The conversion of alcohol to aldehyde, which involves the oxidation process, depends on the class of the alcohol used and the strength of the oxidizing agent. For instance, primary alcohol will form an aldehyde when treated with a weak oxidizing agent; however, it gets over-oxidized to a carboxylic acid in the presence of a strong oxidizing agent. Hence, a mild oxidant like pyridinium chlorochromate is used to convert primary alcohols to aldehydes.
Similarly, Swern and Dess&#8211;Martin oxidations, which employ weaker oxidizing agents, convert primary alcohols to aldehydes. The strength of the oxidizing agent is irrelevant when converting secondary alcohol to a ketone. Both mild and strong oxidants give ketones from secondary alcohols.
Unsaturated hydrocarbons like alkenes undergo an ozonolysis reaction to give aldehydes and ketones. The product formed depends on the substitution present across the double bond in an alkene. A monosubstituted alkene forms formaldehyde and another aldehyde molecule. However, disubstitution gives rise to two cases. A 1,1-disubstituted alkene upon ozonolysis forms a mixture of formaldehyde and ketone, while a 1,2-disubstituted alkene yields a mixture of aldehydes. Both aldehydes and ketones are formed when trisubstituted alkenes undergo ozonolysis, while tetrasubstituted alkenes form ketones exclusively.
Alkynes&#160;also form aldehydes and ketones under hydroboration-oxidation and acid-catalyzed hydration reaction conditions. The hydroboration-oxidation reaction favors anti-Markovnikov&#8217;s addition. Hence terminal alkynes form aldehydes, and internal alkynes&#160;yield ketones. On the other hand, the acid-catalyzed hydration reaction follows Markonikov&#8217;s addition, and thus both terminal and internal alkynes generate&#160;ketones.

Alkollerden, Alkenlerden ve Alkinlerden Aldehitlerin ve Ketonların Hazırlanması

Aldehydes and ketones are prepared from alcohols, alkenes, and alkynes via different reaction pathways. Alcohols are the most commonly used substrates for ...

Aldehitler ve Ketonlar

Preparation of Aldehydes and Ketones from Nitriles and Carboxylic Acids

Although it is possible to reduce a carboxylic acid to an aldehyde, strong reducing agents, like lithium aluminum hydride (LAH), prohibit a controlled reduction, instead causing the generated aldehyde to instantly over-reduce to a primary alcohol.
Reducing carboxylic acid derivatives like acyl chlorides (RCOCl), esters (RCO2R&prime;), and nitriles (RCN) using milder aluminum hydride agents like lithium tri-tert-butoxyaluminum hydride [LiAlH(O-t-Bu)3] and diisobutylaluminum hydride [DIBAL-H] allows the easy conversion of the derivative to the corresponding aldehyde. This is because alkylaluminum hydrides are less reactive than LAH, as the former is more sterically hindered.
According to recent studies, a reductant like diphenylsilane in combination with an air-stable Ni precatalyst and dimethyl dicarbonate as an activator converts most of the carboxylic acid to the aldehyde without causing any over-reduction.
In other studies, a hydrosilane through visible light photoredox catalysis efficiently reduces carboxylic acids to aldehydes.
Ketones, unlike aldehydes, can be directly prepared from carboxylic acids using organolithium reagents. The acid rapidly reacts with two equivalents of an organolithium reagent to form a dianion. This dianion gets protonated to form the corresponding hydrate, which loses a water molecule to give a ketone.
Both aldehydes and ketones can be prepared from nitriles using suitable reducing agents. Aldehydes are formed by the partial reduction of nitriles in the presence of DIBAL-H. The nitrile first forms an aluminum complex, which later, on hydrolysis, yields the corresponding aldehyde. Nitriles can be reduced to ketones via imine intermediates using Grignard or organolithium reagents.

Nitriller ve Karboksilik Asitlerden Aldehit ve Ketonların Hazırlanması

Although it is possible to reduce a carboxylic acid to an aldehyde, strong reducing agents, like lithium aluminum hydride (LAH), prohibit a controlled ...

Preparation of Aldehydes and Ketones from Carboxylic Acid Derivatives

Aldehydes are more reactive than carboxylic acids and hence, can get over-reduced to alcohol in the presence of strong reducing agents. Therefore, carboxylic acids are&#160;inefficient in preparing aldehydes using LAH.
Carboxylic acid derivatives like acid chlorides and esters are more easily reducible than the corresponding acids. The derivatives reduce in the presence of mild reducing agents to give aldehydes. Aldehydes can also be prepared by Rosenmund reduction, that is, the reduction of acid chloride via hydrogenation over a poisoned catalyst. Catalytic poisoning inhibits the over-reduction of aldehydes. A Grignard reagent reduces an acid chloride to tertiary alcohol via a ketone intermediate. The reaction can be stopped at the ketone stage using a milder reducing agent like the Gilman reagent (R2CuLi). Aryl ketones can be prepared by Friedel&#8211;Crafts acylation&#160;in which acid chloride is treated with benzene and AlCl3.
Another carboxylic acid derivative, an ester, can be reduced to an aldehyde using DIBAL-H at dry ice temperature to give an aldehyde. Ketones cannot be prepared directly from esters because ketones are more reactive than esters and tend to over-reduce to tertiary alcohol.

Karboksilik Asit Türevlerinden Aldehit ve Ketonların Hazırlanması

Aldehydes are more reactive than carboxylic acids and hence, can get over-reduced to alcohol in the presence of strong reducing agents. Therefore, ...

Reactions of Aldehydes and Ketones: Baeyer&ndash;Villiger Oxidation

Baeyer&#8211;Villiger oxidation converts aldehydes to carboxylic acids and ketones to esters. The reaction uses peroxy acids or peracids and is often catalyzed by acid. The reaction is named after its pioneers, Adolf von Baeyer and Victor Villiger. The reaction is achieved by a wide range of peracids such as m-chloroperoxybenzoic acid (mCPBA), perbenzoic acid (C6H5COOOH), peracetic acid (CH3COOOH), hydrogen peroxide (H2O2), and tert-butyl hydroperoxide (t-BuOOH).
The carbonyl center is activated by protonating the carbonyl oxygen. The peracid then adds across the C=O bond to give a tetrahedral intermediate called the Criegee intermediate. During the concerted intramolecular rearrangement that follows, the carbonyl group is restored, a group migrates from carbon to oxygen, and the weak peroxide bond cleaves to give an acid (if the substrate is an aldehyde) or an ester (if the substrate is a ketone).
<img alt="Figure1" src="/files/ftp_upload/12341/12341_PT_Figure_1.svg" style="text-align: center; height: 275px;" />
The migratory aptitude of different groups follows the order of &#8211;H &#62; &#8211;CR3 &#62; &#8211;CHR2 &approx; &#8211;Ph &#62; &#8211;CRH2 &#62; &#8211;&NoBreak;CH3. This makes Baeyer&#8211;Villiger oxidation regioselective. Also, the reaction retains the stereochemistry at the migrating center for asymmetrical substrates. Reactions involving cyclic ketones produce lactones.

Reactions of Aldehydes and Ketones: Baeyer&amp;#8211;Villiger Oxidation

Aldehitlerin ve Ketonların Reaksiyonları: Baeyer-Villiger Oksidasyonu

Baeyer&#8211;Villiger oxidation converts aldehydes to carboxylic acids and ketones to esters. The reaction uses peroxy acids or peracids and is often ...

&alpha;-Hydroxy Ketones via Reductive Coupling of Esters: Acyloin Condensation Overview

The pinacol and McMurry reactions involve the reductive coupling of ketones or aldehydes. Similarly, the bimolecular reductive coupling of two ester molecules in the presence of sodium metal in an aprotic solvent yields an &#945;-hydroxy ketone product. The &#945;-hydroxy ketone is also called acyloin, so the reaction is referred to as &#8216;acyloin condensation.&#8217;
<img alt="Figure1" src="/files/ftp_upload/12908/12908_PT_Figure_1.svg" style="text-align: center; height: 65px;" />
In the acyloin condensation reaction, esters are converted to ketyls, which undergo radical dimerization to form an unstable tetrahedral intermediate. Further, this intermediate collapses to give a 1,2-diketone intermediate. The 1,2-diketones are comparatively more reactive than ketones towards electrophiles and reducing agents because of lower &#960;* energy. Consequently, two electrons sequentially transfer to the 1,2-diketone to form an enediolate. Lastly, the enediolate intermediate is quenched with acid to yield an &#945;-hydroxy ketone with a good yield.
Often some by-products are obtained alongside the major product because of the reactivity of nucleophilic enediolate. To overcome the side reactions and improve the yield of an acyloin, trimethylsilyl chloride is used to silylate the enediolate. This results in a bis-silyl ether, further hydrolyzed with aqueous acid to give &#945;-hydroxy ketones.

&amp;#945;-Hydroxy Ketones via Reductive Coupling of Esters: Acyloin Condensation Overview

Esterlerin İndirgeyici Bağlanması Yoluyla α-Hidroksi Ketonlar: Aylloin Yoğunlaşmasına Genel Bakış

The pinacol and McMurry reactions involve the reductive coupling of ketones or aldehydes. Similarly, the bimolecular reductive coupling of two ester ...

Radikal Kimya

Alkylation of &beta;-Ketoester Enolates: Acetoacetic Ester Synthesis

Acetoacetic ester synthesis is a method to obtain ketones from alkyl halides and &beta;-keto esters. The reaction occurs in the presence of an alkoxide base that abstracts the acidic proton of the &beta;-keto esters. The step results in an enolate ion which is doubly stabilized. The enolate then reacts with an alkyl halide via the SN2 process to produce an alkylated ester intermediate with a new C&#8211;C bond. The hydrolysis of the intermediate, followed by acidification, results in an alkylated &beta;-keto acid. Under high-temperature conditions, the &beta;-keto acid undergoes decarboxylation to form a ketone. However, if the alkylation is repeated before hydrolysis and decarboxylation steps, a disubstituted ketone is obtained.

Alkylation of &amp;#946;-Ketoester Enolates: Acetoacetic Ester Synthesis

β-Ketoester Enolatlarının Alkilasyonu: Asetoasetik Ester Sentezi

Acetoacetic ester synthesis is a method to obtain ketones from alkyl halides and &beta;-keto esters. The reaction occurs in the presence of an alkoxide ...