could you please explain 1) a, b, and c? and why is the correct answer for a 136

Question

could you please explain 1) a, b, and c? and why is the correct answer for a 136 instead of 137? can you show a step by step how the go 5 carbons and how did they get nitrogen and chlorine for C?

1) Pick the choice that best answers the following questions bromobutane would have olecular ion(M+) in its mass spec of i) 138 m/z ii) 136 iii) 137 m/z iv) 135 m/z b) According to the following MS data m/z Relative height 100 5.6 74 0.1 is compound contains i) 4 carbons ii))5 ca ons iii) 6 carbons iv) 7 carbons c) c According to the following MS data Relative m/z height 100 133 134 32.6 13 2.3 136 0.1 137 in a This compound contains nitrogen and chlorine chlorine iima bromine iii) a nitrogen

Explanation / Answer

a) For 2-bromobutane exact mass = 135.9888 ( check from chem draw). So, the molecular ion peak which is given by m/z will be = 135.9888/1 = 135.9888 almost equal to 136. 137 is the molecular weight which is not seen in mass spectrum.

b) The molecular ion peak is at 72 as it is showing 100 % relative height. The molecular ion corresponds to entire mass of the molecule. If there were 6 carbons, it would account for the entire mass (6x12 = 72). But that is not possible. There must be hydrogens present in the structure i.e. the molecular ion would be CH3CH2CH2CH2CH2+ (C5H12) with m/z = 72. So, there cannot be just 6 carbons in the molecular ion. To account for the hydrogens, there must be 5 carbons,

c) Third part is confusing. I am sorry I am not sure.

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