查看完整版本 : 關於ether 變ester既mechanism ?

tc121091 2013-5-10 08:28 PM

關於ether 變ester既mechanism ?

如題

[img]http://i690.photobucket.com/albums/vv268/tc121091/question_zps37cbc514.jpg[/img]

我估 Ether 應該唔會有reaction, 應該係第2 part 起reaction 整product ?
但唔知個mechanism 點..

thx :smile_40:

jmlo 2013-5-10 11:14 PM

回覆 1# 的帖子

Hint: Intramolecular cyclization ... :smile_40:

tc121091 2013-5-11 03:13 PM

我估:

左邊個ether 做到acidic cleavage, 變做alcohol
跟住alcohol 同carboxylic group 做 intramolecular estherification

Am I right:smile_41:

jmlo 2013-5-12 01:54 AM

回覆 3# 的帖子

On the right track. There are several things to consider:

(1) What is the possible nucleophile that induces the acidic cleavage of ether?
(2) Which ether O will be protonated?
(3) How does the subsequent intramolecular esterification proceed?

Could you please draw a proposed mechanism? :loveliness:

tc121091 2013-5-14 01:01 AM

[quote]原帖由 [i]jmlo[/i] 於 2013-5-12 01:54 AM 發表 [url=http://www.discuss.com.hk/redirect.php?goto=findpost&pid=361212346&ptid=21887417][img]http://www.discuss.com.hk/images/common/back.gif[/img][/url]
On the right track. There are several things to consider:

(1) What is the possible nucleophile that induces the acidic cleavage of ether?
(2) Which ether O will be protonated?
(3) How does the su ... [/quote]
[img]http://i690.photobucket.com/albums/vv268/tc121091/DSC_0055_zps6d81a862.jpg[/img]

jmlo 2013-5-14 03:55 AM

回覆 5# 的帖子

Recall that a generic acid is used in the reaction; therefore you can't expect the conjugate base (which is presumably H2O) will act as a good nucleophile strong enough to break the ether C-O bond. Moreover, the intramolecular H transfer between OH groups lacks a driving force, and it does not occur often, if not completely impossible. Finally, it seems the H+ in and H+ out of the mechanism is not fully balanced.
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