ippie

ippie
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#1. How many signals and how do they split? (especially Hydrogen 2)
=> Answer : the acidic proton is too removed from the methy hydrogens to exert significant spin-spin coupling effects. also, hydrogen atoms atached to oxygen atoms undergo rapid exchange under most conditions. the net effect is the absence of spin-spin coupling in the signal between the hydroxyl proton and others. I don't really understand the answer. anybody expalin?

#2. How many signals and how do they split? (especailly Hydrogen 3)
=> Answer : same as above.

#3. n-propyl chloride + KOH (alc) --> ??
=> I think SN 2 occurs, but the answer said Elimination occurs. I think the answer is wrong. am I right?

#4. CH3CHICH2CH3 + NaOH (aq.) --> ??
=> I thought the answer is E2, buth the answer said all the result of SN1, SN2, E1 and E2 can occur. why? does real DAT give us this kind of vague question?
 

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doc3232

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Feb 15, 2008
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picture is attached. please check.

#1. How many signals and how do they split? (especially Hydrogen 2)
=> Answer : the acidic proton is too removed from the methy hydrogens to exert significant spin-spin coupling effects. also, hydrogen atoms atached to oxygen atoms undergo rapid exchange under most conditions. the net effect is the absence of spin-spin coupling in the signal between the hydroxyl proton and others. I don't really understand the answer. anybody expalin?

#2. How many signals and how do they split? (especailly Hydrogen 3)
=> Answer : same as above.

#3. n-propyl chloride + KOH (alc) --> ??
=> I think SN 2 occurs, but the answer said Elimination occurs. I think the answer is wrong. am I right?

#4. CH3CHICH2CH3 + NaOH (aq.) --> ??
=> I thought the answer is E2, buth the answer said all the result of SN1, SN2, E1 and E2 can occur. why? does real DAT give us this kind of vague question?
First one, I don't know if this sounds far-stretched but keto-enol form might have an effect. I have never seen a carboxylic doing keto-enol though. Also the carboxylic might deprotonate and not show up on the NMR.
Second, sort of answered from first
Third, Agree with you, but that type of question is actually asking which is the major product, so both do form to an extent.
Fourth, It is very unfair to say all occur because when you think about it, there are millions (I am exaggerating) of reactions taking place in a beaker of those 2 and all 4 types do occur. Specifically for secondary carbons (everything and anything happens).
I hope I helped and I don't think DAT would be vague, I would think they would be the 100% opposite where only 1 reaction in fact occurs.
GOOD LUCK
 

Orgodox

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#4)I agree that the fourth is vague.

#1 )I learned that the hydroxyl proton of carboxylic acids displays a resonance signal significantly down-field of other functions. For a typical acid it appears from 10.0 to 13.0 δ and is often broader than other signals. So Im not sure why they are saying here it wont show up at all. I agree that it may undergo exchange with the other oxygen but I dont see why it wouldnt show a signal if that is the case.

2) I would say #1 1=singlet 2=singlet downfield #2 1=triplet 2=quartet 3=singlet most downfield

3) I would say it would be E2. Its a stong base (stronger base than it is a nucleophile). Keep in mind that Sn2 and E2 are in competition here though.
 
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ippie

ippie
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orgodox! even if it's strong base, substrate is primary RX. As long as the base is not bulky, SN 2 occurs. If the base is strong and bulky in primary RX, E2 occurs. rigiht?