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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: 113zami on June 21, 2008, 10:56:29 AM

Title: rank the following aromatics according to bacisity?
Post by: 113zami on June 21, 2008, 10:56:29 AM

http://i274.photobucket.com/albums/j...mi/acidity.jpg

can you please help me with this question, I got it up to

strongest---->weakest
A,  B,  C,  D,  E

please let me know if this answer is correct, and also I am not sure if C comes before D or D comes before C??

thanks

Title: Re: rank the following aromatics according to bacisity?
Post by: macman104 on June 21, 2008, 11:13:23 AM

There is no image at that link.

Title: Re: rank the following aromatics according to bacisity?
Post by: 113zami on June 21, 2008, 11:35:51 AM

http://i274.photobucket.com/albums/jj243/113zami/acidity.jpg

zoom in if some parts are cut

Title: Re: rank the following aromatics according to bacisity?
Post by: sjb on June 21, 2008, 11:47:49 AM

What is a base (in this context)? What factors will influence its strength?

Title: Re: rank the following aromatics according to bacisity?
Post by: 113zami on June 21, 2008, 11:59:29 AM

a base is something that has an electron donating group attached to the benzene, and an acid is something that has an electron withdrawing group attached, e- withdrawing goups make the benzene more acidic and e- donating groups make benzene more basic

Title: Re: rank the following aromatics according to bacisity?
Post by: 113zami on June 22, 2008, 10:44:45 AM

I am still stuck on this :(, can someone PLEASE help me, i don't know if C comes before D or the D comes before C, please help thanks

Title: Re: rank the following aromatics according to bacisity?
Post by: alexanderdundua on June 22, 2008, 12:08:09 PM

Quote from: 113zami on June 22, 2008, 10:44:45 AM

I am still stuck on this :(, can someone PLEASE help me, i don't know if C comes before D or the D comes before C, please help thanks

C comes after D.

Title: Re: rank the following aromatics according to bacisity?
Post by: macman104 on June 22, 2008, 01:10:03 PM

The focus of the bascisity is not on the hydrogens of the benzene.  You are exploring the effect of various groups on the amine's basicity.

If the amine picks up a hydrogen, it is going to have a positive charge.  Using various inductive and resonance effects, you should explore which groups stabilize this positive charge the best.

Also, some groups may push electrons into the amine, thus increasing the availability of the amines electron pair.

Title: Re: rank the following aromatics according to bacisity?
Post by: Beatle on June 27, 2008, 11:25:27 PM

I thought the methyl group would cause that compound to be the most basic for starters

Title: Re: rank the following aromatics according to bacisity?
Post by: vhpk on June 28, 2008, 10:54:47 PM

I think the most basic is B because -CH₃ is an electron donator, the next is D because -Cl is in meta position,hence it causes less effect than C when Cl is in ortho position more convinient to deactivate benzene ring, O is more electronegative then Cl so it diperse more negative charge on N atom, A ranked the fourth, and E is the most acidic because there is a negative charge on the benzen ring

Title: Re: rank the following aromatics according to bacisity?
Post by: Dan on June 29, 2008, 06:50:31 AM

Remember to consider resonance. Although O is electronegative, it is a donating group by resonance, and this is often dominates inductive effects. With the OH in the ortho position I would also consider stabilisation of the conjugate acid by hydrogen bonding in addition to resonance effects.

I expect A is more basic than B.