Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Dolphinsiu on March 30, 2007, 08:23:38 AM
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Deduce a structure consistant with the following data
C = 58.38%, H = 9.80% (C:H = 1:2)
(EI) m/z (abundance %): 207 (10), 205 (30), 204 (12), 192 (15), 190 (45), 170 (10), 164 (11), 162 (33), 157 (11), 156 (100)
(207:205 = 1:3, Cl is existed, 205 imply at least one N, 205 - 156 = 49 imply -CH2Cl fragmentation. The overall formula is C10H20NOCl)
IR (cm-1) : 2900, 1650
1H NMR (CDCl3):
1. 0.9 (6H,d)
2. 1.0 (6H,d)
3. 1.1 (3H,d)
4. 2.3 (1H,m)
5. 2.5 (2H,m)
6. 3.5 (2H, bd)
What I predict is:
(3)
CH3 CH3 O
l l ll
(H3C)2 - N - CH2 - C - C - C - CH2Cl
l l
CH3 H
(2) (5) (1) (4) (6)
Does my prediction have problems?
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Does my prediction have problems?
I'm afraid so. I don't have time to check this in detail right now, but...
Your structure is not consistant with your formula (no N in the structure).
You have a C with a valency of 5.
CH3 CH3 O
l l ll
(H3C)2 - CH2 - C - C - C - CH2Cl
l l
CH3 H
IR does not support the presence of a ketone. Looks like an amide.
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Sorry! I have not typed N (typing mistakes)
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O
ll
If 1650 really imply - C - N (CH3)2
Fragmentation of -CH2Cl is still correct!
Then
I will predict
(4)
CH3 H O
l l ll
Cl - CH2 - C - C - CH2 - C - N - (CH3)2
l l
CH3 CH3
(6) (1) (3) (5) (2)
Is my second prediction close to yours?
But from Mass spectrum
190 and 162 imply the loss of 15(CH3) and 43(COCH3) respectively!
So I still don't know the actual structure!
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I don't think that structure accounts very well for the nmr data. The methyl groups on N would peak at higher ppm, and the splitting patterns are not consistent with that structure.
I haven't come up with anything that gives a good correspondance to the nmr data either. Are you sure that both 6H, d are in fact doublets and not two singlets?
ie. is it possible that 6H, d is actually 2 x 3H, s?
Can you get any more info on the structure of the multiplets?
Also, 43 in the MS could be an isopropyl group, Me2CH. An isopropyl group may also be responsible for a 6H, d in the nmr.
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I just copy from my past paper. I also don't have any idea in this question! Actually I am weak in predicting the unknown cpds!