Question

STRUCTURE DETERMINATION PROBLEMS USING IR AND PROTON NMR SPECTROSCOPY

Determine the structure of the six compounds whose IR and PMR spectra are provided on the attached sheets, given the following comments about the provided information and spectra.

PMR Spectra: The PMR spectrum of each compound is provided, along with peak areas. The peak areas are given as the simples whole number ratio of protons and are indicated (for exmpale, 4H). Your final structure must be consistent with the chemical shift speak areas and splitting pattern. show which protons in the molecule are responsible for each set of peaks.

Molecular formula: The molecular formula is given in the upper right hand corner of each sheet. you dont need the MW or Percent by weight information

IR spectra: The abosrption frequencies printed on the IR spectra are in cm

MF C10H14 MW 134 %C 89.5 %H 10.5 2000 1880 MeVENUBERS 3H 5H 2H 2H 2H 7.4 7.2 7.0 6.a 6.6 6.4 6.2 PPM Proton NMA 3.0 1.5 1.0 PPM 0.5 2.5 2.0

Answer 1

Answer As per given molecular formula CiH14 Degree of unsaturation (DOE) exists in the given molecular formula: (10 1) 14/2 4 As we know when the DOE is equal or greater than 4, the structure is aromatic. As per the given 'H-NMR spectra, 5H present in aromatic region: СlоНа — СаН,— С,Н, Aliphatic protons given in H-NMR spectra 2H (t) — СH 2H (m CH2 2H (m) CH Зн (() — СН, Structure of the compound: 1.3-1.5 0.90 Нас-сн,-сн-CHз SH (m) 7.0-7.5 H H As per the given IR spectra: 3000 3100 cm1 - = C-H stretching of alkene 1634.98 cm 1454 cm C-H bending of alkane (methyl group) 744.8 cm-long chain methyl C-C stretching of alkene