Name: alkyl halide reduction with tributyltin hydride
Uploaded: 2023-04-30T11:22:27.000Z
Duration: 1 min 26 s
Channel: JoVE

Radikal ikame reaksiyonları, alkanların ve alkenlerin halojenasyonu için faydalıdır.
Benzer şekilde, radikal ikameler, alkil halojenürlerin hidrojenolizi olarak bilinen tribütiltin hidrit kullanarak alkil halojenürlerden halojeni uzaklaştırabilir.
Özellikle, kalay hidrit zayıf bir Sn-H bağına sahiptir ve halojeni hidrojen ile değiştirmek için alkil halojenürlerle reaksiyona girerek alkan ve kalay halojenür oluşturabilir.
Oluşan yeni bağlar kırılan bağlardan daha güçlü olduğu için reaksiyon enerjik olarak tercih edilir.
Hidrojenoliz mekanizması bir zincirleme reaksiyonu takip eder.
Başlangıçta, kalay hidrit, ışığın varlığında bir tribütiltin radikali üretir, bu daha sonra halojeni bir organik halojenürden soyutlar ve radikal bir ara ürün üretir.
Daha sonra, radikal ara ürün, hidrojeni kalay hidritten soyutlar ve sonunda reaksiyonu yayan bir alkan ve bir tribütiltin radikali oluşturur. 
Alkil halojenürlerin hidrojenolize doğru reaktivitesi, alkil florürlerin reaktif olmadığı iyodürden florüre azalır.
Özellikle, alkil klorürlerin indirgenmesi, reaksiyona AIBN gibi bir başlatıcı eklenerek elde edilen daha yüksek bir tribütiltin radikalleri konsantrasyonu gerektirir.

radikal sübstitüsyon: alkil halojenürlerin tributiltin hidrit ile hidrojenolizi

Radical Substitution: Hydrogenolysis of Alkyl Halides with Tributyltin Hydride

Fonksiyonel grupları moleküllerden uzaklaştırmak için radikal ikame reaksiyonları kullanılabilir. Alkil halojenürlerin hidrojenolizi, tributiltin hidritteki zayıf Sn-H bağının alkanlar oluşturmak üzere alkil halojenürlerle reaksiyona girdiği böyle bir reaksiyondur. Burada Bu_3SnH reaktifi, bir yan ürün olarak tributiltin halojenürü verir.

Bu reaksiyonda oluşan bağlar, kırılan bağlardan daha güçlüdür ve bu da onu enerji açısından olumlu kılar. Reaksiyon, radikal halojenasyon reaksiyonlarına benzer bir radikal zincir mekanizmasını takip eder; burada Bu_3SnH, bir tributiltin radikali oluşturmak için ışık varlığında homolitik bölünmeye uğrar. Bu radikal, halojeni bir alkil halojenürden ayırarak bir alkil radikal ara maddesi ve tributiltin halojenür oluşturur. Radikal ara ürün ayrıca tributiltin hidritten hidrojeni uzaklaştırır ve reaksiyonu ilerleten bir alkan ve bir tributiltin radikali üretir.

C-Br ve C-I bağları C-Cl bağlarından daha zayıf olduğundan alkil bromürlerin ve iyodürlerin hidrojenolizini başlatmak için gün ışığı yeterlidir. Buna karşılık alkil florürler, güçlü C-F bağları nedeniyle reaktif değildir. Alkil klorürlerin Bu_3SnH kullanılarak hidrojenolizi, reaksiyon karışımına bir başlatıcının eklenmesiyle elde edilen yüksek konsantrasyonda tributiltin radikalleri gerektirir. AIBN, nitril ile stabilize edilmiş radikaller oluşturmak üzere 60 °C'nin üzerinde termal homolize uğradığından en yaygın kullanılan başlatıcıdır. Bu radikaller tributiltin hidritten hidrojeni uzaklaştırarak reaksiyonun ilerlemesini sağlayan tributiltin radikalini oluşturur.

<img alt="Figure1" src="/files/ftp_upload/12901/PT_12901_Figure%201.svg" style="text-align: center; height: 190px;">

Peroksit radikalleri oldukça reaktif olduğundan ve organik halojenürlerden hidrojeni ayırıp istenmeyen yan reaksiyonlara yol açabileceğinden, peroksitler başlatıcı olarak kullanılmaz.

Radikal Sübstitüsyon: Alkil Halojenürlerin Tributiltin Hidrit ile Hidrojenolizi

Radikal ikame reaksiyonları, fonksiyonel grupları moleküllerden çıkarmak için kullanılabilir. Alkil halojenürlerin hidrojenolizi böyle bir reaksiyondur, burada ...

radical-substitution-hydrogenolysis-alkyl-halides-with-tributyltin

Education

JoVE Core

Organic Chemistry

Organik Kimya

Unit 1

Ünite 1

Radical Chemistry

Radikal Kimya

KEY TERMS AND CONCEPTS

TEMEL TERİMLER VE KAVRAMLAR

alkyl halide reduction with tributyltin hydride

Alkyl halide reduction with tributyltin hydride removes a halogen and replaces it with hydrogen. This reaction turns alkyl halides into alkanes. The reagent Bu3SnH has a weak Sn–H bond, and the reaction forms tributyltin halide as a byproduct. Because the new bonds are stronger than the bonds that are broken, the reaction is energetically favorable.

The reaction proceeds by a radical chain mechanism, which is similar to radical halogenation. Light causes Bu3SnH to split homolytically, meaning the bond breaks evenly to form a tributyltin radical. That radical removes the halogen from the alkyl halide. This step creates an alkyl radical intermediate and tributyltin halide.

Next, the alkyl radical takes hydrogen from tributyltin hydride. This forms the alkane product and a new tributyltin radical. The new radical then continues the chain reaction.

Bond strength affects how easily the reaction starts. C–Br and C–I bonds are weaker than C–Cl bonds, so daylight can start the hydrogenolysis of alkyl bromides and iodides. Alkyl fluorides do not react because C–F bonds are very strong.

Alkyl chlorides need more tributyltin radicals, so an initiator is added to the reaction mixture. AIBN is the most common initiator. Above 60 °C, it undergoes thermal homolysis and forms nitrile-stabilized radicals. These radicals remove hydrogen from tributyltin hydride and create the tributyltin radical that keeps the reaction going.

Peroxides are not used as initiators in this reaction. Their radicals are very reactive and can remove hydrogen from organic halides. That can lead to unwanted side reactions.

Alkyl Halide Reduction with Tributyltin Hydride

alkyl-halide-reduction-with-tributyltin-hydride

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Alkyl halide reduction with tributyltin hydride removes a halogen and replaces it with hydrogen. This reaction turns alkyl halides into alkanes. The reagent Bu3SnH has a weak Sn–H bond, and the reaction forms tributyltin halide as a byproduct. Because the new bonds are stronger than the bonds that are broken, the reaction is energetically favorable. The reaction proceeds by a radical chain mechanism, which is similar to radical halogenation. Light causes Bu3SnH to split homolytically, meaning...

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key terms and concepts

Learn how tributyltin hydride removes halogens from alkyl halides through a radical chain reaction, and why light, AIBN, and bond strength matter.

Alkyl Halide Reduction with Tributyltin Hydride | JoVE K12

organic chemistry

JoVE Core Organik Kimya, kısa ve anlaşılması kolay animasyonlu video dersleri kullanarak stereokimya, reaksiyonlar ve mekanizmaların temel kavramlarını açıklar. Buna ek olarak, bilim insanlarının yer aldığı videolar, ilgili kavramların günümüz laboratuvarlarında gerçekleştirilen klasik ve orijinal araştırma deneylerinde nasıl uygulandığını göstermektedir.

Alkyl Halide Reduction with Tributyltin Hydride

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