118 - Practice Problem 1-18 Answer Each compound gives only...

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Practice Problem 1-18 Answer Each compound gives only one signal in its 1 H-NMR spectrum. Approximately where on the chemical shift scale would you expect this signal to appear? All chemical shift ranges are reported relative to TMS. (a) Cyclohexane 1.2 1.4 (aliphatic protons) (b) 2.1 2.3 (adjacent to sp2 hybridized carbonyl C atom) (c) 6.5 8 (aromatic protons) (d) CH 2 Cl 2 4.5 6 (2 electron-withdrawing Cl atoms are attached to the same carbon) (e) (CH 3 ) 3 N 2.5 4.5 (adjacent to electron-withdrawing N atom) Practice Problem 1-19 Answer Identify the different kinds of nonequivalent protons in the following molecule, and tell where you would expect each set to absorb on the chemical shift scale. The nonequivalent sets are labeled with letters. Expected chemical shifts (relative to TMS) for each set are indicated below. a = 3.3 4.0 (adjacent to O) e = 4.5 6.0 (aromatic) b = 6.5 8.0 (aromatic) f = 1.5 2.5 (allylic) c = 6.5 8.0 (aromatic) g = 1.0 1.5 (aliphatic) d = 4.5 6.0 (vinylic) Practice Problem 1-20 Answer Predict the splitting patterns you would expect for each type of proton in the following molecules: In each part, the different types of protons are labeled with letters. (a) CHBr 2 CH 3 a = quartet; b = doublet (b) a = doublet; b = septet; c = quartet; d = triplet C H 3 C CH 3 O H 3 CO H H C H H C CH 2 CH 3 H H a b b c c d e f g a b a a b c d
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(c) CH 3 OCH 2 CH 2 Br a = singlet; b = triplet; c = triplet (d) a = triplet; b = quartet; c = septet; d = doublet (e) ClCH 2 CH 2 CH 2 Cl a = triplet; b = quintet (f)
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118 - Practice Problem 1-18 Answer Each compound gives only...

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