2 Which of the following would not have a CH stretch at abou

2. Which of the following would not have a C-H stretch at about 3050 cm1 A) 1-pentene B) 2-pentene 2-methyl-2-pentene 2,3-dimethyl-2-pentene E) 2,4-dimethyl-2-pentende 3 Explain the following observation regarding the IR stretching frequencies of the ketones shown belovw 1685 cm 1710 cm 4. Account for fragments having a m/z value of 45 and 55 in the mass spectrum of 2-hexanol by drawing structures of the fragments what compound has a significant m70 in its mass spectrum? A)1-pentanol B) 2-butanol C) diethyl ether D) octane E) (E)-2-pentene 6. The mass spectrum of alcohols often fail to exhibit detectable Mt peaks but instead show relatively large AM+1 B)M+2 C)M-16 D) M-17 )M-18 peaks The mass spectrum of which compound has an M+2 peak that has intensity that is about 4% of its Mr peak? 3CH2)2S B) (CH3CH2)20 sider 3-pentanone (shown below). What m\'z fragments would you expect to see in the mass spectrum ot 43 57 D) You would expect to see all three fragments. me Page 1 1

Solution

2) In IR spectra ,CH stretching vibrations below3000cm-1 is for the presence of saturated carbons(CH3-,-CH2-,CH-) of alkyl groups.But C-H stretch below 3000 cm-1 is for unsaturated CH=C-

Among the given compounds,

1) CH2=CH-CH2-CH2-CH3 (1-pentene)

2) CH3CH=CH-CH2-CH3(2-pentene)

3) CH3C(CH3)=CH-CH2-CH3 (2-methyl-2-pentene)

4) CH3C(CH3)=C(CH3)-CH2-CH3(2,3-dimethyl-2-pentene) no =CH present ,so it does not show peak at 3050cm-1

5)CH3C(CH3)=CH-CH(CH3)-CH3(2,3-dimethyl-2-pentene)