سؤال لعباقرة الكيمياء العضوية ارجو المساعدة

[eman omar osman]

ارجو مساعدتى فى فهم هذا التفاعل
R-CO-CH2-CO-CH3 + Br2/NaOH.......................>R-COCH2COONa + CHBr3 (bromoform reaction)
بينما فى حالة اجراء التفاعل فى
acidic medium
RCO-CH2CO-CH3 + Br2/Acetic acid ..........................> RCOCHBr2
لماذا تمت الdeacetylation ????????

 

[waleed_hamoda]

بسم الله الرحمن الرحيم

السلام عليكم ورحمة الله وبركاته

خدى التفاعلات دى مبدأياً على ما آجى ان شاء الله نشوف الحكاية من كتاب فينر

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[abu-omar]

The first reaction is the called iodoform test and is special for carbonyl compounda having methylgroup attached to the carbonyl group directly
The second reaction is halogenation of carbonyl compunds
the details are found in any organic textbook
see in this site Morrisn , McMurry or March

 

[waleed_hamoda]

These Reactions in details​

Title
Alpha Halogenation of Ketones
Caption
When a ketone is treated with a halogen and base, an a-halogenation reaction occurs.
Notes
The reaction is called base-promoted, rather than base-catalyzed, because a full equivalent of the base is consumed in the reaction.
Keywords
alpha halogenation, base-catalyzed, base-promoted​

http://upload.arabsbook.com/userfiles/vb/25578_1207665083.jpg
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Title
Mechanism of Haloform Formation
Caption
The trihalomethyl ketone reacts with hydroxide ion to give a carboxylic acid. A fast proton exchange gives a carboxylate ion and a haloform.
Notes
When chlorine is used, chloroform is formed; bromine, bromoform; iodine, iodoform.
Keywords
trihalomethyl ketone, haloform, chloroform, bromoform, iodoform​

http://upload.arabsbook.com/userfiles/vb/25578_1207665242.jpg
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Title
Bromoform Reaction
Caption
A methyl ketone reacts with a halogen under strongly basic conditions to give a carboxylate ion and a haloform.
Notes
The trihalomethyl intermediate is not isolated. Iodoform is a yellow solid and its formation is used as a qualitative test for methyl ketones.
Keywords
trihalomethyl ketone, haloform, iodoform​

http://upload.arabsbook.com/userfiles/vb/25578_1207665354.jpg
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Title
Mechanism of Acid-Catalyzed a-Halogenation
Caption
The mechanism of acid-catalyzed halogenation involves attack of the enol form of the ketone on the electrophile halogen molecule. Loss of a proton gives the haloketone and the hydrogen halide.
Notes
Acidic halogenation may replace one or more a-hydrogens depending on how much halogen is used.
Keywords
a-halogenation​

http://upload.arabsbook.com/userfiles/vb/25578_1207665421.jpg
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from this site as a reference
http://wps.prenhall.com/wps/media/objects/340/348272/wade_ch22.html
........​

 

[waleed_hamoda]

See Also This PDF Link
http://www.4shared.com/file/4344455...loform_reactions.html?dirPwdVerified=98cdd41d
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[eman omar osman]

اشكركم جميعا على المساعدة
و لكن اريد ان اعرف لماذا التفاعل الاول تم على ال methyl
بينما تم التفاعل على ال methylene فى acetic acid
هل هذا له علاقة بقدرة ال bromine على التفاعل حسب ال PH

 

[eman omar osman]

ولماذا تمت ال deacetylation فى الحالة الثانية

 

[waleed_hamoda]

فيه كذا حاجة عندك فى المركب

أولاً: ال-CH2- التى تتوسط ال المجمعوتين -CO- تحمل labile Hydrogen أى يسهل خروجها بكل سهولة

وبذلك المركب يوجد فى صورة enol form

ثانيا: أكيد زى ما الوسط الحمضى والقاعدى بيأثر على الكيتون البسيط زى ما فى الأمثلة اللى فوق ...
أكيد بردك بيأثر على الداى كيتون وبيدى النتيجة اللى حضرتك حاطتها فوق

ثالثاً: حاول تربط كل التفاعلات اللى فوق مع بعضها وملف البيدى اف هتوصل لنتيجة ان شاء الله
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