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Pupil
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Respect (86%):
Date Posted: 7/25/2008 12:08:57 AM  Status: Closed
arrange the following in order of decreasing acidity
Course Textbook Chapter Problem
Organic Chemistry N/A N/A N/A
Question Details:
put most acidic first
 
1. benzoic acid 2. benzyl alcohol 3. phenol 4. ethanoic acid
 
the options are 3,1,2,4
3,2,1,4
4,1,3,2
4,1,2,3
2,1,4,3
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Answers:

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(CUNY Queens College)
Date Posted: 7/25/2008 12:38:09 AM  Status: Live
Asker's Rating: Helpful   
Response:
Benzoic acid > Phenol > benzyl alcohol  > ethanoic acid
 
Acidity depend on the on the resonance. The more resonance the more acidity. Here, benzoc acid has the most resoance. Phenol has more resonance than benzyl alcohol.
RDWAN

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Date Posted: 7/25/2008 12:59:26 AM  Status: Live
Asker's Rating: Lifesaver   
Response:


acidity is based on the formation of the alkoxide or phenoxide ions

activators lower the acidity because they are  electron donating and deactivatorss are electron withdrawing weakening the hydrogen bond making it slighty postive which helps in the formation of the alkoxide or phenoxide ion

easier way is activators are anti acidic and deactivators make more acidic

also phenols are resonance stabillized making them more acidic than alcohols

so in order of highest acidity to lowest

1 >4>3>2

and the prior post is wrong ethanoic acid has a pKa of 4.76 way lower than Phenols which is 9.89

*(there must be something wrong with your answers because benzoic acid has pka of 4.21 which makes it more acidic than ethanoic acid)

just so you have no doubts i'm wrong here is why

ranked in order of acidity

1 ( pKa= 4.21)  > 4 (pKa=4.76) > 3 ( pKa= 9.89) > 2( pKa= 15)

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