Acidity of compounds

[RHONDAROBINSON]

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I know that alcohol is more acidic than any other compound. What is the range of increasing acidity or decreasing acidity of compounds. Is it phenol, alcohol,????? Thanks


rr

 

[haavoc]

Usually, electron withdrawing groups (o/p or m-deactivators) are responsible for increasing the acidity of a compound.

For example:

p-nitrobenzoic acid is quite acidic as well as m-fluro benzoic acid.

The Kaplan blue book has a nice section which has all the electrophillic substitution activators and deactivators.

 

[RHONDAROBINSON]

Activating, ortho/para directing substituents (electron-donating): NH2,NR2,OH,NHCOR,OR, OCOR, and R.

Deactivating,orth/para-directing substituents(weakly electron-withdrawing): F,Cl,Br, and I

Deactivating,meta-directing substituents(electron-withdrawing): NO2,SO3H, and carbonyl compounds, including COOH,COOR,COR,and CHO.

Stating these facts, which group of hydrocarbons displays decreasing strength of acidities?

A. phenol,ethanol,acetylene,ethane
B. ethane,phenol, ethanol,acetylene
C. acetylene,ethane,phenol,ethanol
D. ethanol,acetylene,ethane,phenol
E.ethanol,phenol,acetylene,ethane

THANKS
.

 

[Cher*]

Stating these facts, which group of hydrocarbons displays decreasing strength of acidities?

A. phenol,ethanol,acetylene,ethane
B. ethane,phenol, ethanol,acetylene
C. acetylene,ethane,phenol,ethanol
D. ethanol,acetylene,ethane,phenol
E.ethanol,phenol,acetylene,ethane

THANKS
.[/QUOTE]


the answer is A, here is why:


phenol is the most acidic in this list, because if you take its acidic H away, the negative charge can be delocalized through the aromatic ring

ethanol is weakly acidic because if you remove its acidic H, the negative charge goes on oxygen; since there's no way it can delocalize the acidity is less than that of phenol

acetylene has an acidic H bonded to C with the triple bonds (HCCH); this means if acetylene is put into a basic solution, its acidic H can be dissociated (same holds true for the other above WEAK acids)

and finally ethane is not acidic because it doesn't really contain any acidic H, and it's put into a basic solution, CH3CH2:- will NOT form

 

[RHONDAROBINSON]

Thanks for the help. Where did you get this information? My organic chemistry is weak.

rr

 

[Cher*]

No problem!

I actually just took my dat yesterday, so I was pretty much prepared!

I have been studying for a while, and after lots of practice, you'll get the hang of it so don't give up! I used kaplan to kinda refresh my memory about the stuff I need to practice on. topscore, acheiver, and destroyer are all great tools to use. destroyer, especially, is a great problem set to do when you are ready for it.

I did well in my ochem (25) and science sections, so let me know if you have any questions. 😉

 

[RHONDAROBINSON]

Hello Cher,

Did your test on yesterday have lots of reactions in Organic Chemistry? In order to get that 25 in Organic Chemistry how did you learn all the reactions? What was your study routine in detail?Do you think that the test was similiar to the DAT Achiever or easier? Thanks in advance.


rr

 

[Cher*]

hey rr

first, i did the kaplan practice tests, which was ok. but I think if you know the roadmaps in the destroyer and understand all the problems in there, u should do fine. U can also make flashcards if u think that would help you. make sure to take advantage of the achiever too. the actual dat was easier than acheiver so don't be bummed if u don't do so well on acheiver.

there were couple of direct and indirect questions on sn1/sn2/e1/e2 so make sure to know everything about those types of reactions. reduction/oxidation questions are also typical so know those as well.
gl 😉

 

[RHONDAROBINSON]

Cher,

On the SN1,SN2,E1,E2 reactions, where the questions asking about the solvents that are good, which nucleophile is good,reactivity with the substrates as to what kind is used(such as 3>2>1>CH3), which reaction is preferred over the over? Did the test have lots of aromaticity and telling what the products is of the following reaction? I am asking this because my Organic is weak. Thanks in advance.

rr

 

[Kami]

Can anyone tell me that there are two different Kaplan DAT books and which one is the better one. Is it the one that is Kaplan DAT second edition or the one that is Kaplan DAT 2007-2008 edition.

Thanks

 

[RHONDAROBINSON]

I am not sure if the two books are different. But I went to Barnes and Noble to check the new blue Kaplan book with Review Notes from Kaplan from 1998 and the information is the same word from word. The review notes that were written 8 years ago is just the same as the new blue book. So, the books you are speaking of may not be that different except for the CD.

rr