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Register a new userInversion of Reactivity (umpolung) of Carbonyl Compounds Using Organosulfur Compounds Reagents
انقلاب فعالية المركبات الكربونيلية باستخدام مركبات الكبريت العضوية
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Tishreen University ورقة بحثية
Publication date
2018
fields
Chemistry
and research's language is
العربية
Authors
عبد الكريم الحمد( باحث )
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Shamra Editor
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استخدمت مركبات الكبريت العضوية في انقلاب فعالية المركبات الكربونيلية ،حيث تحث الذرات الغير متجانسة المرتبطة في السلاسل العضوية فعالية محددة لذرات الكربون في المركب المدروس ، تكون الذرات الغير متجانسة أكثر كهرسلبية من الكربون (-I effect)، و تأثيرها الميزوميري المانح (+M effect) يساهم في تثبيت الشحنة الموجبة على ذرة الكربون المجاورة ذات الطبيعة الآخذة. تهاجم الكواشف النيكليوفيلية المواقع في المركبات الكربونيلية. بينما تهاجم الكواشف الالكتروفيلية المواقع ,يتم تغيير الطبيعة الالكترونية للمواقع سابقة الذكر عن طريق تحويل زمرة الكربونيل الى زمرة اسيل تكون فيها ذرة الكربون ذات طبيعة مانحة. بعد إجراء التحولات السابقة من الضرورة أن يكون تفاعل إعادة تشكيل زمرة الكربونيل سهلاً. أطلق D.Seebach على ما تمثله العمليات السابقة مصطلح كلمة umpolung
Organosulfur compounds have been exploited to reverse the reactivity of carbonyl compounds. The heteroatom produces a reactivity pattern in a carbon skeleton. Its electronegativity, being greater than that of carbon (-I effect) and its ability to stabilize an adjacent positive charge (+M effect) makes the sites susceptible to be attacked by reagents possessing a given “philicity”. Nucleophiles attacks the odd C atomes ( 1,3,5... C attack) whereas electrophiles attacks the even C atomes ( 2,4,6... C attack) of the carbonyl compounds. If the reactivity of a carbonyl could be reversed, the acyl carbon would become nucleophilic, and if this transformation can be accomplished, the carbonyl should be regenerated. Seebach termed this process ''umpolung''.
References used
E.J.Corey, pure. Appl. Chem,14, 1967 , 19
D.A.Evans and G.C.Andreus, Accounts. Chem. Research, 7, 1974,147
D.Seebach, Angew. Chem. Int.Ed.Engl, 18, 1979,239
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