Doc Brown's Chemistry  Molecular structure deduction - 3 problems to solve

NMR problem solving with associated molecular data

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These questions illustrate how you can unite various sources of data-information to deduce the structure of a molecule

You will need tables of nmr chemical shifts and

characteristic infrared absorption frequencies (as wavenumber cm-1)

Atomic masses: C = 12, H = 1, O =16  *  Answers to NMR problems

KS4 Science GCSE/IGCSE Revision Qualitative Analysis Quiz on chemical test methods for identifying ions, gases and compounds

Qualitative Analysis * Quantitative analysis: acid-base, silver nitrate-chloride, EDTA titrations * Quantitative analysis: Redox titrations


NMR PROBLEM 1 with associated infrared spectrum, molecular ion and % element by mass data

nmr problem 1 % mass element analysis:

82.76% C and 17.24% H

Infrared spectrum:

Peaks in 2850-2950 cm-1 region

NO suggestion of any specific functional group absorption

Molecular ion peak from mass spectrometry: 58

NMR PROBLEM 2 with associated infrared spectrum, molecular ion and % element by mass data 

nmr problem 2 % mass element analysis:

54.55% C, 9.09% H and 36.36% O

Infrared spectrum:

sharp strong absorption at 1735-1750 cm-1

NO broad absorption band from ~2500-3200 cm-1

Molecular ion peak from mass spectrometry: 88

NMR PROBLEM 3 with associated infrared spectrum, molecular ion and % element by mass data

nmr problem 3 % mass element analysis:

62.07% C, 10.34% H and 27.59% O

Infrared spectrum:

strong sharp absorption at 1700-1725 cm-1

moderate, broad absorption at ~2450-3150 cm-1

Molecular ion peak from mass spectrometry: 116

 

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