Perform all routine operations:(a) Determine the molecular weight from the Mass Spectrum.(b) Determine relative numbers of protons in different environments fromthe 1H NMR spectrum.(c) Determine the number of carbons in different environments and thenumber of quaternary carbons, methine carbons, methylene carbons andmethyl carbons from the l3CNMR spectrum.Chapter 8 Determining the Structure of Organic Compounds from Spectra(d) Examine the problem for any additional data concerning compositionand determine the molecular formula if possible. From the molecularformula, determine the degree of unsaturation.(e) Determine the molar absorbance in the UV spectrum, if applicable.(2) Examine each spectrum (JR, mass spectrum, UV, l3CNMR, 'H NMR) in turnfor obvious structural elements:(a) Examine the IR spectrum for the presence or absence of groups withdiagnostic absorption bands e.g. carbonyl groups, hydroxyl groups, NHgroups, C=C or C=N, etc.(b) Examine the mass spectrum for typical fragments e.g. PhCHz-, CH3CO-,CH3- , etc.(c) Examine the UV spectrum for evidence of conjugation, aromaticrings etc.(d) Examine the lH NMR spectrum for CH3- groups, CH3CHz- groups,aromatic protons, -C~X, exchangeable protons etc.(3) Write down all structural elements you have determined. Note that some aremonofunctional (i.e. must be end-groups, such as -CH3, -C=N, -NOz) whereassome are bifunctional (e.g. -CO-, -CHz-, -COO-), or trifunctional (e.g. CH, N).Add up the atoms of each structural element and compare the total with themolecular formula of the unknown. The difference (if any) may give a clue tothe nature of the undetermined structural elements (e.g. an ether oxygen). Atthis stage, elements of symmetry may become apparent.(4) Try to assemble the structural elements. Note that there may be more thanone way of fitting them together. Spin-spin coupling data or informationabout conjugation may enable you to make a definite choice betweenpossibilities.(5) Return to each spectrum (JR, UV, mass spectrum, l3CNMR, lH NMR) in turnand rationalise all major features (especially all major fragments in the massspectrum and all features of the NMR spectra) in terms of your proposedstructure. Ensure that no spectral features are inconsistent with your proposedstructure.Note on the use of data tables. Tabulated data typically give characteristic

absorptions or chemical shifts for representative compounds and these may notcorrelate exactly with those from an unknown compound. The data contained in datatables should always be used indicatively (not mechanically).