[shona788]

It is given that 2-chloro-3-methylpentanamide undergoes further reaction while 3-methylpentanamide doesn't

I have proposed a mechanism for this reaction but i am not sure if it is correct.
The molecules were initially acyl chlorides which were reacted to ammonia to give the amide and then heated.

I am unsure about the role of the extra chlorine atom in 2-chloro-3-methylpentanamide as compared to 3-methylpentanamide, if it is wrong, i'll need a hint cause i'm lost in that

[Dan]

It is given that 2-chloro-3-methylpentanamide undergoes further reaction

Further reaction under what conditions? Can you post the question in full?

The mechanism you have is dodgy. Note that it is not balanced, which is a good indication that you're doing something wrong.

C₆H₁₂ClON -> C₆H₁₄ClON

General advise: follow your curly arrows, watch your charges and don't skip intermediate structures. However, I don't think you're on the right track here, but we need to know the context in which "further reaction" occurs.

[shona788]

here is the full question

Account for the fact that compound G is unreactive when using ammonia at high temperatures whereas compound H gives a cycloadduct under similar conditions.
Predict the possible product in the reaction



I guess that firstly, ammonia will attack the carbony C but then i don't know what difference will the Cl  make

[shona788]

the molecules are acyl chlorides, i missed the chlorine atoms at the end in the structures....

[orgopete]

I am going to try to change this problem somewhat as I don't think it makes sense as stated. Compound G gives G' when reacted with ammonia and H gives H'. Compound H' gives a cycloadduct when heated while G' does not.

I expect compounds G and H to react with ammonia without heating. I'm thinking of a dimer, C12H26N2O2.

[shona788]

I have tried to propose this mechanism but i'm unsure if chlorine can attack the carbonyl carbon

I thought about this since chlorine is nucleophillic, bearing a delta - and the carbonyl c bears a delta +

But is this a proposable mechanism?

[Arctic-Nation]

No, your mechanism has three major flaws in it. The first is that you do an impossible reaction on the alpha-chloroamide, the second is the elimination of hydroxide when chloride would be a much better leaving group, and the third is a thermal [2+2] cycloaddition of alkenes.

Alpha-halocarbonyl groups are particularly effective electrophiles on the alpha carbon atom. Orgopete hinted at dimerization, which would certainly be a possibility (though my solution gives C12H22N2O2 instead of H26) with the incomplete structure. Taking into account the diphenylvinyl group, however, you've got a strong electrophile and a reasonable nucleophile which can combine together into a six-membered ring.

Though obviously, I might be wrong.

[orgopete]

Let me give a correction to my earlier MF. I did it without looking at the actual structures. I see there are two phenyl groups attached to the alkene. The dimer I was thinking of should have MF C46H46N2O2 and a further hint, a diketopiperazine.

[Doc Oc]

No, your mechanism has three major flaws in it. The first is that you do an impossible reaction on the alpha-chloroamide, the second is the elimination of hydroxide when chloride would be a much better leaving group, and the third is a thermal [2+2] cycloaddition of alkenes.

Alpha-halocarbonyl groups are particularly effective electrophiles on the alpha carbon atom. Orgopete hinted at dimerization, which would certainly be a possibility (though my solution gives C12H22N2O2 instead of H26) with the incomplete structure. Taking into account the diphenylvinyl group, however, you've got a strong electrophile and a reasonable nucleophile which can combine together into a six-membered ring.

Though obviously, I might be wrong.

I would agree with this, although 5-membered rings close faster than 6-membered rings.  Also, the carbon that would be required to form a 6-membered ring is stabilized particularly well, and not as good of a nucleophile in my opinion.

[Arctic-Nation]

Well nutbunnies. 5-membered it is, somehow added an extra carbon atom when drawing it out on paper. The tertiary carbocation is the obvious intermediate.