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Anonymous asked in 科學化學 · 1 decade ago

Anomer effect?

Glucose與CH3OH+H+反應後,產生Anomer effect是什麼?

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  • 1 decade ago
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    所謂的anomer是指醣類化合物中α,這種異構物的情形,由於立體位向不同在anomeric center,所以稱之anomer。

    如:

    圖片參考:http://img.tfd.com/dorland/anomer.jpg

    The α- and -anomers of glucose: (A) α-d-glucopyranose; (B) -d-glucopyranose. The hydroxyl group of interest is indicated by the yellow boxes.

    我想你問的應該是anomeric effect:

    一般cyclohexan這種chair form構型的化合物,在axial位置會比較不穩定。

    但是在醣類分子上,由於環上有O,不是單純的碳鍊六環,所以O上會有lone pair donate到一號碳的σ*的空軌域上,而產生多餘的穩定能。

    此多餘的穩定能,會使得醣類分子在αform(就是在axial)的情形較為穩定,所以稱之為anomeric effect。

    圖片參考:http://www.casper.organ.su.se/thesis/anomer1.gif

    而你的問題中: Glucose與CH3OH+H+反應後,應該會在一號C上引入OCH3基團,而依據anomeric effect,你會得到αform較多的產物。

    Source(s): 我的知識
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