Question

parent ion at m/z 102 (M*), IR peaks at 1740 and 1150 cm 10. Propose a structure for a molecule whose mass spectrum shows which gave the following 'H NMR spectrum.) 6 1 septet 2 5 0 6 PPM 11. Propose a structure for a molecule whose mass spectrum shows a parent ion at m/z 116 (M*) with at 1740 and 1150 cm1 which gave the following H NMR spectrum. base peak at m/z 43, IR peaks 6 1 2 3 PPM 12. Propose a structure for a molecule whose mass spectrum shows at 1740 and 1150 cm1 which gave the following 1H NMR spectrum. parent ion at m/z 116 (M*) with base peak at m/z 43, IR peaks 6 1 O 3 PPM

Answer 1

I. R. peaks at 1740 1740cmt indicates & stretching 11 socl indicated -c-o stretching High value for & stretching & poesence of -C-o bond indicate that compound may contain-2-o- NMR data: 2 4.9, 1H, septet CH @ 1.3, 6H, doublet ->24.c group h 43 CH3b Hoç na + 1 = 1+1=2 doublet not1 = 6+1= ? septet 2.2, 3H, singlet-- CH adjacent to an ortom without Hatoms.

from NMR the following groups ax present HC-CH-CH₂ & CH₂ These two account for 43+15= 58 Molecules mas = 102 Remaining narx 102 - 58= 44 from I.R. we know the presence op & o-group. This for 44 accounts 28 +16 present are groupe . The HC - CHI - CH₂ - Co- By get combining these units we will following two structures

1740 11 sont - CH - Cor CH₂ - should have high s value should have nearly 3.9 &value near to but given 2.3 2.3 but given.4.9 give so this structure doesn't dvaluer. satisfying 1940cm! insomt s. 2.2, 3H, singlet 24 ) T 4.9,1H, seplet 1.3, 6H, doublet structure, I is the correct Iso propyl Acetate

O - U 1740cmt - team - 1150 cm! -, 7 0 4 S -C-o- 44 Esle NMR data: 04.2, 2H, ③ 1.3, 3H - quartet toiplet CH₂ adj to CH₂ CH₂ adj to CH₂ There two poerence of signal, indicate the - CH₂ - CH₂ group. - CH₂ - CH₂ 3H 2H, triplet quarter 2.7, 1H, septet CH adj to 6H 1.2, 6H, doublet 20Hz adj to CH There two signals indicate poerente of Isopropyl group the

2.7TH, Seplet Y 1.2, 6H, doublet NMR, the two from unite prevent are CH₂ - CH₂ - ¢ B C CH - 43 72 There two account for 29+43= Molecules max is 116. so semaining mass 116- 72 = 44 -&o- from I.R.) This 44 accounts for - The units are - CH-, le-CH2- - "-o- these units we By combining will get

-CH2 CH2- CA, - Céo - CH - CH3 Should have svalue in the sange sepp but givers 4.2 I should have d value in the sange x 4ppm but given 2.7. so this structerse is not the values. so this is not required structase. Let us another possibility satisfying the toy 1740cm e CH 11 5ocm 5) 4.2, 2H, 2.1.14 GH septet doublet triplet Ethyl-2-methylpropanoat

L2) 17 4 cr) - 7 7) CO 1150 m! c-O ma ss - 44 from NMR : -1) 4.9, 1H, seplet, CH adjacent to 6H or 2 CH₃ ( ) 1.4, 6H doo bet 2CH3 groups adjacent to CH group. C olet x 4.9, 1H, seplet. 1.4, 6H, doublet is present. so 9 so propyl group at 43 also confirm, peak Base this group. HC- & - 43

at 3 2.3, 2H, quartet 10 1.2, 3H, triplet H₂ adj. to CH₂ the These presence two of signals indicate CH₂ - CH2 group. following from I. R. & N.HR data units are present CH₂ - CHE, CHo 43 - 2943 HC- CH - OJ 44 29+43 +44 = 116 combining we will get By Isepropyl poopanoate 4-9H CH 3 + ho cha 6 or CH 3 1-2,34 23,24,9 9 CH2 hc - CH₂ - 0 is correct which sattefte, &values CH - CH₂