Question

Use the data below from an electron impact mass spectrum of a pure compound to deduce its structure. Draw your structure in the drawing window.

Data selected from the NIST WebBook, http://webbook.nist.gov/chemistry/

m/z	Relative intensity
66	32
64	100
49	26
29	72
28	83
27	60                                         I wrote it is a 5 membered ring with double bond on two sides but it is incorrect Use the data below from an electron impact mass spectrum of a pure compound to deduce its structure. Draw your structure in the drawing window. Data selected from the NIST WebBook, http://webbook.nist.gov/chemistry/ m/z Relative intensity 110 59 108 60 81 8 79 9 29 100 28 29 27 95 26      44 Use the data below from an electron impact mass spectrum of a pure compound to deduce its structure. Draw your structure in the drawing window. Data selected from the NIST WebBook, http://webbook.nist.gov/chemistry/ m/z Relative intensity 73 1.0 72 25 57 8 43 100 29 17

Answer 1

(1) Interpretation of the given information:

m/z of M⁺ (molecular ion peak) = 64 (indicates molecular mass of the molecule is 64)

m/z = 66 indicates the M+2 due to isotope

Relative intensity of M⁺ and M+2 (i.e., 100:32), indicates the presence of Cl atom in the molecule. For Cl, M:M+2 is 3:1.

Peak at m/z = 29 is due to loss of Cl atom (Base peak is given by loss of halogen)

Peak at m/z = 49 is due to loss of -CH3

The structure of the molecule is CH₃CH₂Cl

(2) Interpretation of the given information:

m/z of M⁺ (molecular ion peak) = 108 (indicates molecular mass of the molecule is 108)

m/z = 110 indicates the M+2 peak due to isotope

Relative intensity of M⁺ and M+2 (i.e., 60:59), indicates the presence of Br atom in the molecule. For Br, relative intensity ratio M:M+2 is 1:1.

Peak at m/z = 29 is due to loss of Br atom (Base peak due to loss of halogen)

The structure of the molecule is CH₃CH₂Br (Ethyl bromide)

(3) Interpretation of the given information:

m/z of M⁺ (molecular ion peak) = 72 (indicates molecular mass of the molecule is 72)

m/z = 73 indicates the M+1 peak due to isotope

Relative intensity of M⁺ and M+1 (i.e., 25:1), indicates the M+1 peak is due to isotope of carbon.

Peak at m/z = 57 is due to loss of -CH3

Peak at m/z = 43 is due to loss of CH2 from the ion at m/z = 57 (This is the base peak)

Peak at m/z = 29 is due to further loss of -CH2

The structure of the molecule is CH₃CH₂CH₂CH₂CH₃ (Pentane)