Question

Name: Starting with the mass spectrum of n-heptane What is the molecular ion? What fragment is lost to generate the ion with m/z =71? What cation does the peak at m/z = 43 represent? What group does the spacing between each set of ions represent? Why is the peak at (M-15), corresponding to loss of -CH3 so small? Draw the structure of 2,4-dimethylpentane What is the structure of the ion responsible for m/z = 85? Relative Intensity What is the structure of the ion responsible for m/z = 57? 10 20 30 40 50 70 80 0 100 60 m/z What is the structure of the ion responsible for m/z = 43?

Answer 1

structure of n-heptane : thC ECH) CH3 I ion in mass spectra Molecular ion :- The heaviest is called molecular ion. In n-heptane, the molecular ion peak is at too (III) The ethyl (CH-CH) fragment is lost to generate con with m12 =71 C A C- CH₂ m/2=29 CH - C4 C4 C -C43 mize 71 1 the propyl casion mlz = 43. C chach-eh) does the peak at The each - CH2 - group (m/2= 14 set of ion. does the spacing between I peak at n=15 corresponding to loss of - CH₂ so small because - o oue to loss of methyl group, slightly hexyl carion is formed having m/2=85. i co choch-ch-oh-uh- CH₂ 1 m/2=15 m/2-85

@ structure of 2,4-dimethylpentane H₂C - CH CH CH CH₂ - CH3 CH₂ @ structure of ion m/2=85 is are Hz C-CH-CH₂-CH-CH3 CH3 Do The structure of ion for m12=57 and 43 . C- CH - Chef CH-CH3 m/2=57 57 miz= 43 12 = 43 of carbo cations - 3 » Resonance contributions Alcohol / Ethey :- 2) Thiols/ Thioethers :- 3) Amines :- RI

Molecular ion peak is the heaviest ion peak.

6 ostructure of 2-methylpenten-3-01 нс - си- сн— CH, CH, сна од The m/2 = 73 structure of ion at Ңс- сн — су си, ои 1 The structure of ion for peak at m/2=59 си — он, — и,