OCHEM question~

ippie · Jul 9, 2006

what is the product of the following reaction?

n-propyl chloride + KOH ---> ?

A. isopropyl chloride
B. isopropyl alcohol
C. n-propyl alcohol
D. propylene
E. 2-chloro-1-propanol

The answer is D. Why not C?
The reaction is about the primary halide and the strong base, so Sn 2 occurs.
Even if KOH is strong base, it' not bulky, so E2 cannot occur. Only strong and bulky such as KOt make the reaction E2 in primary halide reaction. Am I wrong? Please explain me.

digdig · Jul 9, 2006

ya u are right. that answer is wack.

Dentizt · Jul 10, 2006

digdig said:
ya u are right. that answer is wack.

Correct answer is D. Check out http://www.cem.msu.edu/~reusch/VirtTxtJml/alhalrx3.htm
for proof.

ippie · Jul 15, 2006

Is this table right?
This table is a little different from the table that Kaplan gave me.
I always solved the problem based on that table of Kaplan.
And I always got right.
Especially, in the primary halide, KOH is only strong base, not the bulky.
The base that has characteristic of both strong and bulky can make the reaction occur E2. Am I wrong? please, explain me.

Dentizt said:
Correct answer is D. Check out http://www.cem.msu.edu/~reusch/VirtTxtJml/alhalrx3.htm
for proof.

SundevilDMD · Jul 15, 2006

A strong base ALWAYS favors E2 over SN2. SN2 is favored by strong nucleophiles (weak bases).

ippie · Jul 15, 2006

Sundevil, I am sorry, i don't understand.
The strong base always favors E2. It's true only in secondary and tertiary alkyl halide.
But in primary alkyl halide, the strong base always favors SN 2 but if that base is both strong AND (not OR) bulky, E2 occur.
Am I wrong? I still confused.

SundevilDMD said:
A strong base ALWAYS favors E2 over SN2. SN2 is favored by strong nucleophiles (weak bases).

dontbam · Jul 15, 2006

It really doesn't matter, as long as you have a strong base, you're most likely gonna get a E2 reaction. Think of it this way, if you're not given a solvent and you look at the structure, you can almost guess that the rxn is gonna be E2!

ippie said:
Sundevil, I am sorry, i don't understand.
The strong base always favors E2. It's true only in secondary and tertiary alkyl halide.
But in primary alkyl halide, the strong base always favors SN 2 but if that base is both strong AND (not OR) bulky, E2 occur.
Am I wrong? I still confused.

asckwan · Jul 15, 2006

I'm sorry but I don't think that's true. If it's primary and a strong small base, SN2 usually wins unless there is heat added to the reaction, then it will be likely to be an E2. I don't agree with the answer given. I referenced my text and it seems as it agrees with ippie's reasoning.

cali99boy · Jul 17, 2006

what about steric hindrance due to the angle?

I also got D and figured that -OH would pluck off that H and form that double bond.

Notoriousjae · Jul 17, 2006

asckwan said:
I'm sorry but I don't think that's true. If it's primary and a strong small base, SN2 usually wins unless there is heat added to the reaction, then it will be likely to be an E2. I don't agree with the answer given. I referenced my text and it seems as it agrees with ippie's reasoning.

He is right. the answer should be C and not D.
for SN2: 1>2>3 favors primary
for E2: 3>2>1 favors tertiary
since propyl chloride is a primary alkyl halide, the answer would be a n-propyl alcohol by an Sn2 substitution reaction.
I'm not sure if E2 wins over Sn2 if heat is applied but i think that kind of depth of information might not be needed for the actual DAT. Its good to know it nonetheless. cheers!

SgtSadhu · Jul 17, 2006

if the KOH is in alcohol solution it will go e2

OCHEM question~

ippie

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Dentizt

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Notoriousjae

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