Read More
Date: 1-8-2019
1136
Date: 26-11-2019
885
Date: 3-8-2019
758
|
Whether 1,2 or 1,4-addition occurs depends on multiple variables but mostly it is determined by the nature of the nucleophile. During the addition of a nucleophile there is a competition between 1,2 and 1,4 addition products. If the nucleophile is a strong nucleophile, such as a Grignard reagent, both the 1,2 and 1,4 reactions are irreversible and therefore are under kinetic control. Since 1,2-additions to the carbonyl group are fast, we would expect to find a predominance of 1,2-products from these reactions.
If the nucleophile is a weak base, such as alcohols or amines, then the 1,2 addition is usually reversible. This means the competition between 1,2 and 1,4 addition is under thermodynamic control. In this case 1,4-addition dominates because the stable carbonyl group is retained.
Water
Alcohols
Thiols
1o Amines
2o Amines
HBr
Cyanides
Gilman Reagents: These act as a source of R:–
Example
|
|
دراسة يابانية لتقليل مخاطر أمراض المواليد منخفضي الوزن
|
|
|
|
|
اكتشاف أكبر مرجان في العالم قبالة سواحل جزر سليمان
|
|
|
|
|
اتحاد كليات الطب الملكية البريطانية يشيد بالمستوى العلمي لطلبة جامعة العميد وبيئتها التعليمية
|
|
|