Альфа-ефект

Альфа-ефект, α-ефект (рос. α-эффект[эффект Хайна] , англ. α-effect [Hine effect]) — підвищення нуклеофільності карбаніона або гетероатома під впливом безпосередньо зв'язаного з таким центром атома, який має неподілену пару електронів (O, N, F, Cl)[1], напр., у NH2NH2, NH2 OH. Цей ефект проявляється в додатньому відхиленні величин logknuc для нуклеофілів, які мають неподілену пару електронів на атомі сусідньому з нуклеофільним центром, від залежності типу Бренстедта:

logknuc = F(pKa),

побудованої для серії звичайних нуклеофілів.

Більш загально, це вплив атома, що має неподілену пару електронів на реактивність сусіднього з ним реакційного центра.

Використання терміна набуло поширення на ефекти будь-якого замісника при сусідньому до реакційного центра атомі, наприклад, «α-силікон ефект». Синонім — ефект Хайна.

Література

Примітки


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