Answers to Problems
Chapter 1
3.
6.
7.
8.
Gamma rays > X-rays > UV > Visible > IR > Radio waves
(a) (i) 4000 cm- 1
(ii) 35087.7 cm- 1
(iii) 3355.7 cm- 1
(b) 7.495 x 108 MHz to 3.748 x 108 MHz
(a) 7.15 kcal/mole
(b) 1.499 x 10 15 cps to 0.7495 x 1015 cps
(a) 47.67 kcals mole- 1 or 199.45 kilo Joule mole- 1
(b) 4000 cm- 1 to 666.67 cm- 1
(c) 24.176 x 10 13 cps (Hz) or 24.176 xl07 MHz
Chapter 2
2.
5.
8.
9.
(J' ~ er* > n ~ (J'* > n ~ n* > n ~ n*
n ~ n* < n ~ n* < n ~ er*
(a)
A, 1,4-Pentadiene; B, cis-1,3-pentadiene and C, trans-1 ,3-pentadiene
(iii) 226 nm
(ii) 342 nm
249 nm
(i)
(vi) 239 nm
(v) 280 nm
(iv) 418 nm
(iii) 285 nm
(ii) 269 nm
254 nm
12. (i)
15. a < d < b < c
(c) 254 nm
(b) 315 nm
259nm
17. (a)
19. (d)
20. A is 1,3-cyclohexadiene and B is 1,4-cyclohexadiene.
21. (b)
22. 285 nm and 257 nm
24. (a) 2-propanol, ethanol, heptene, water and dioxane
26. Structure (a) is correct.
28. p-benzoquinone
(ii) n-n*
29. (i) n-n*
30. (i) 229 nm (ii) 323 nm
(iii) 351 nm (iv) 281 nm
Chapter 3
Rotational < Vibrational < Electronic
I. (b)
(iv) 12
(iii) 7
(ii) 21
4. (i) 9
(v)
1
5. (i) Esters
(ii) Acid halides
Answers to Problems
9.
12.
14.
15.
16.
19.
20.
21.
22.
24.
26.
28.
30.
31.
+ 317
(iii) Amides
(iv) Anhydrides
(a) p-aminoacetophenone < acetophenone < p-nitroacetophenone
(b) cyclohexanone < cyclopentanone < cyclobutanone
(B) CH2=CH-CH 20H
(A) CH3COCH3
(b) > (a)
(i) b < a < c
(ii) (b) < (c) < (a)
CH 3CH 2CONH2
trichloroacetic acid < chloroacetic acid < acetic acid < ethanol
(i)
3300 cm- 1 (Ya-H• hydrogen bonded)
(ii) 3050 cm- 1 (Yc-H• aromatic ring)
(iii) 2990 cm- 1 (Yc-H methyl group)
(iv) 1700 cm- 1 (Yc=O• hydrogen-bonded ester)
(v)
1540 and 1590 cm- 1 (Yc-a. aromatic ring)
C6H5CH 20H
CH 3COCH3
C6H5CHO < CH 3COCH 3 < CH 3CHO < CH 3COCJ
(iii) Inactive
(i)
Inactive
(ii) Active
(iv) Active
(v) Inactive
(vi) Inactive
Butanone
m-cresol
Benzaldehyde
Chapter 4
5. 5401 A
6. 22.6
7. The energy of radiation (274.49 kJ) is lesser than the dissociation energy of H2,
hence it cannot dissociate.
9. CS 2 has a center of symmetry, whereas N20 has no center of symmetry and thus
the structures must be S-C-S and N-N-0, respectively.
10. The compound has trans and planar structure:
15. 214, 3,11, 454 and 758 cm- 1•
17. (a), (b), (c) and (e) will exhibit both the vibrational and rotational Raman spectra;
(d) will not exhibit rotational Raman spectrum.
18. H2 > HD > D2.
20. (a), (b) and (d) will exhibit rotational Raman spectra; (c) will not exhibit rotational
Roman spectrum.
21. (i) Active (ii) Inactive (iii) Inactive (iv) Active (v) Active
22. The molecule has a trans, planar geometry:
f
Y-Z-Y
I
X
318
+ ORGAN/C SPECTROSCOPY
23. 6688, 7033, 7043 and 7839
24. H3C-C =:C-CH3
A
Chapter 5
1. For 14N, 2H, 35Cl and 31 P NMR spectroscopy is possible.
(c) 3(3 : 2 : 2)
(b) 3(3 : 2 : I)
3. (a) 2(5 : 3)
6. (a) 3; one singlet, one triplet and one quartet
(b) 3; one singlet, one triplet and one quintet
(c) I; singlet
(d) I; singlet
10. Chemical shift positions are 8 5.75 and 8 1.05; lAx= 10 Hz.
11. (a) ClCHzCC1zCH3 (b) C6 H5-(CH3h
(c) C6 H5 -CH 2CH (CH 3)z
12. (a) 1; 3 (3 : 2 : 1) (b) 3 (5 : 2 : 3); 2 (2 : 3)
(c) 4 (3 : 2 : 2 : 3); 2 (3 : 2)
14. C6H5C(CH 3)zCH 2Cl
18. BrCH 2CH 2CH 2Br
(iii) 5.43 8
(ii) 4.78 8
7.52 8
21. (i)
22. (CH3)zCHOH
25. (a)
(CH 3)3COH
26. 3.5 8; 6.51"
27. C6 H5CH 2CH 3
28. CICH 2CH 2COOH
29. p-nitrophenol
31. C6H5 CH 2CH 2 0H
Chapter 6
l. (a) 2, (b) 5, (c) 2, (d) l.
Two peaks; one singlet and one doublet
4. (a)
Three peaks; one singlet, one doublet and one quartet
(b)
One peak; one triplet
(c)
Three peaks; one doublet, one triplet and one quartet
(d)
(CH 3 )zCHC =CH (b) (CH 3CH 2)zCHCH 3 (c) CICH 2CHCICCI 3
5. (a)
8. (CH 3)zCHCOCH3
Six peaks; two singlets, three doublets, and one quartet; the singlet due to
9. (a)
ketonic carbon will have the highest and the quartet the lowest 8 value.
Four peaks, one singlet, two triplets and one quartet; the singlet will have
(b)
the highest and the quartet the lowest 8 value.
Four peaks; one singlet, one triplet and two quartets; the singlet will have
(c)
the highest and the quartet the lowest 8 value.
Three peaks; one quartet and two triplets; the triplet due to C-3 will have
(d)
the highest and the quartet the lowest 8 value.
(CH 3CH 2)JCH (b) CH3CH 2CHOHCH 3
10. (a)
(c)
CH 3C ==CCH 2CH 3
14. (a)
5; one singlet, three triplets and one quartet
(b)
9; four singlets, four doublets and one quartet
(c)
2; one doublet and one triplet
(d)
4; one singlet and three triplets
Answers to Problems
18.
+ 319
~H,
Cl
Chapter 7
I.
3.
5.
6.
(a), (c)
(a) 12, (b) 14, (c) 10, (d) 7
(a) 3; I : 1 : 1 (b) 5; 1 : 4: 6: 4: I (c) 3; I : 2: I (d) 6; 1 : 5 : 10: 10: 5 : I
(a) 7
(b) 8. A, CH(COOH)z; B, CH 2COOH.
(b) 8
9. (a) 35
10. (a) 7; 1 : 6 : 15 : 20 : 15 : 6 :.1
(b) 4; I : 3 : 3 : 1
(c) 7; 1 : 6: 15 : 20: 15 : 6: I
(d) 3; 1 : I : I
12. 0.3319 T
13. (c)
14. C 6 H(;
15. Yes; 2 lines in intensity ratio I : 1
16. 5/2
Chapter 8
2. (i) HC =C-Br (ii) HCOOCH3
+
+
+
+
+
t
9. C 2 H 5 0H, CH 3 CH=OH, CH 2 =0H, C 2 H~. HC;;::O, OH and CH 3
12. CH 3 1
14. n-heptane
Chapter 9
~
CH30\
I.
CH 3
d
CH-CH 2 -C-CH 3
0
2.
II
H 3C-C-CH 2 -CH 2 -COOH
0
3.
H3C-~-C(CH3h
0
4.
II
N-C-CH 2 -C-O-CH 2 CH 3
320. ORGANIC SPECTROSCOPY
6.
CHOHCOOH
I
CHOHCOOH
7. CH 3CH 2C ==CH
8. CH 2 = CH-CH 20H
9.
0
©r
(allyl alcohol or 2-propen-1-ol)
10. CH 3CH 2CH 2C ==CH, the isomer may be CH 3CH 2C ==C-CH3 (other structures
are also possible)
11.
0
CH2CH 20CCH3
II
12. (CH3hCH-O-CH (CH3h
13. CH 3 -CH-COOH
I
Br
14. CH 3CH 2CO-O-COCH 2CH 3
15. (CH 3h CHCONH 2
16. H3C-O-CH 2-C ==N
0
II
17. CH 3CH2CCH3
0
II
18. (CH 3) 3C-OCH3
~CH,OH
19.
20. CH 3COCH 2CH3
0
21.
0
11-@-11C-üCH2CH 3
CH 3CHzQ-C
Index
a, ß-unsaturated carboxylic acids, UV,
34
a,ß-unsaturated esters, UV, 34
y-Gauche steric compression, 210
Absorption bands, 12:
designation of, 13
formation of, 12
Absorption 1aws, 7
Absorption of energy, NMR, 136
Absorption spectra, 5
Acetylenic protons, 147
Acid anhydrides, IR 78
Acid halides, IR 78
Alcohols, IR 69
Aldehydes, IR 72
Aldehydic protons, 148
Alkanes, IR 67
Alkenes, IR 68
Alkyl substituents, 21
Alkynes, IR 69
Allowed transition, 14
Allylic coupling, 167
Amides, IR, 79
Amines and their salts, IR 80
Aminoacidsand their salts, IR, 81
Analysis of NMR spectra, 168
Anisotropie effect, 146
applications of, 92
Aromatic compounds, 40, 41, 42
non-benzenoid, 42
polynuclear, 40
Aromatic coupling, 167
Aromatic hydrocarbons, IR 69
Aromatic protons, 149
Auxochrome, 16
8-Bands, 13
Base peak, 255
Bathochramie shift, 16
Bending vibrations, 56, 57
Benzene and its derivatives, UV 34
Blue shift, 16
13 C chemical shifts, 202, 205, 211
a-, ß- and y-effects, 203
13 C NMR spectroscopy, 195
applications of, 214
common modes of recording, 196
samp1e handling, 196
theory, 195
use of shift reagents, 214
Carbony1 carbons, 210
Carboxylate axions, IR 75
Carboxylic acid, IR 75
Chemical ionization (Cl) method, 251
Chemical shift, 142, 143, 144. 145, 146,
152, 170, 199
Chromophore, 15
Combination bands, 61
Comparison between NMR and ESR.,
243
Conjugated systems, UV, 17
Continuous wave NMR spectroscopy,
184
Coupled vibrations, 62
Coupling constant (1), 164, 165, 166
Cycloalkanes, IR 68
Daughter ions, 253
Deformations, 56
Deshielding, 142, 148, 149, 150
Detection of isotopes, 256
Deuteration, 178
Deuterium exchange, 178
Deuterium labelling, 178
Dicarbonyl compounds, UV, 32
Difference bands, 61
Double irradiation in ESR, 239
Double irradiation, 177
Double resonance in ESR, 239, 240
Double resonance, 177
DSS as reference, 143
322 +Index
E-Bands, 13
ELDOR, 240
Electromagnetic radiations, I, 2
Electromagnetic spectrum, 4, 5
Electron impact (EI) method, 250
Electron paramagnetic resonance (EPR),
224
Electron spin resonance (ESR)
spectroscopy, 224
instrumentation, 227
interpretation, 237
multiple! structures, 232
theory, 224
Electronic spectroscopy, 7, 15
Electronic transitions, 9
cr
~
n
~
cr*, lO
cr*, lO
n ~ n*, 11
n ~ n*, 11
Emission spectra, 5
ENDOR, 239
Epoxides, IR, 71
Equivalent and non-equivalent protons,
153
ESR spectra, interpetation of, 237
Esters, IR, 76
Ethers, IR, 71
Exocyclic double bonds, 21
Fermi resonance, 63
Fine structure, 232
Fingerprint region, 92
First order spectra, 169
Flipping of nucleus, 137
Forbidden transition, 14
Fragment ions, 253
Fragmentalion modes, 262
general, 262
of alcohols, 272
of aldehydes and ketones, 276
of alkanes, 265
of alkenes, 267
of alkynes, 268
of amines, 282
of aromatic hydrocarbons, 269
of carboxylic acids, esters and amides,
278
of ethers, acetals and ketals 275
of halogen compounds 270
of heterocychic compounds, 286
of nitriles 283
of nitro compounds, 284
of phenols, 274
of sulphur compounds, 285
of various classes of compounds, 265
Fragmentalion processes, 262
examples of, 262
factors governing, 262
representation of, 262
Frequency, I
Fundamental vibrations, nurober of, 58
g factor, 226, 227, 229
Gated decoupling, 198
Geminal coupling, 165
Halogen compounds, IR, 69
Heteroannular dienes, 21
Heteroaromatic compounds, UV, 42, 43
Homoallylic coupling, 167
Homoannular dienes, 20
Hydrogen bonding, IR, 64
Hydrogen bonding, NMR, 151
Hyperchromic effect, 16
Hyperfine structure, 233
Hypsochromic shift, 16
Imides, IR, 79
Index of hydrogen deficiency, 258
Inductive effect, IR, 66
Instrumentation of
IR spectroscopy, 52
PMR spectroscopy, 139
Raman, 119
Interpretation of NMR spectra, 168
lonization processes, 250
IR absorption frequencies, table of,
83
IR inactive vibrations, 57, 60
IR spectra, interpretation of, 94
IR spectroscopy, 52, 55, 92
Isotope peak, 256
K-Bands, 13
Ketones, IR, 72
Lactans, IR, 79
Lactones, IR, 76
Long range coupling, 167
Longitudinal relaxation, 139
Magnetic equivalence, 172
Index+ 323
Mass spectroscopy (MS), 250
applications, 260
instrumentation, 253
Mass spectrum, 255
Mesomerie effect, IR, 66
Metastahle ions or peaks, 260
Molar absorptivity, 7
Molecular ion peak, confirmation of,
257
Molecular ion, 252
Multiplicity, 159
Multiply charged ions, 259
Nitriles, IR, 83
Nitrites, IR, 82
Nitro compounds, IR, 82
Nitrogen rule, 258
NMR scale, 144
NMR spectra, 168, 170
ana1ysis of, 168
NMR versus ESR, 243
Non-benzenoid aromatic compounds,
UV, 42
Nuclear Overhauser effect (NOE), 181
Number of PMR signals, 153
Off-resonance decoupling, 197
Olefinic protons, 148
Overtone bonds, 60
Parent ion, 252
Peak area and proton counting, 156
Phenols, IR, 69
Phosphorus compounds, IR, 83
Photon, energy for, 2
Polarization of Raman lines, 118
Poly-ynes, UV, 26
Polyenes, UV, 26
Precessional frequency, 13 7
Proton exchange reaction, 174
Proton nuclear magnetic resonance
(PMR or 1H NMR) spectroscopy,
133
applications of, 181
continuous wave (CW), 184
Fourier transform (FT), 184
instrumentation, 140
sample handling, 140
s1gnals, 153
theory, 133
Proton-noise decoupling, 196
Protons on hetero atoms, 174
R-Bands, 13
Raman effect, I07
theories of, 109
Raman spectra, pure rotational, 115, 116
vibrational, 114
vibration-rotational, 117
Raman spectroscopy, 107, 109, 120
applications, 121
effect, 107,108,109,111,112
instrumentation, 119
origin of, 107
samp1e handling, 121
theories of, 109
Raman tube, 120
Raman versus fluorescence spectra, 124
Raman versus IR spectra, 124, 125
Red shift, 16
Relaxation processes, 139
Resonance effect, IR, 66
Ring residues, 21
Rocking, 57
Rule of mutual exclusion, 118
Sampie handling,
ESR, 231
IR, 54
PMR, 141
Raman, 121
UV, 9
Satellite peak, 256
Saturation, NMR, 138
Scissoring, 56
Second order spectra, 170
Shielding, 142, 147, 149, 151
Shift reagents, 179
Solvent effer, UV, 18
Spectroscopy (spectromctry), dcfinition,
1
Spectroscopy, infrared (IR), 52, 92
Spin lattice relaxation, 139
Spin number /, 133
Spin systems, nomenclature of, 170
Spin-spin coupling, 157, 172
Spin-spin coupling, 13 C, 212
Spin-spin decoupling, 177
Spin-spin relaxation, 139
Spin-spin splitting, 157, 158, 173
Stretching vibrations, 56, 58, 60, 61
Sulphur compounds, IR, 83
324 +Index
Theory of ESR spectroscopy, 224
applications of, 240
Theory (origin) of IR spectroscopy, 55
TMS as reference, 143
Transition probability, 14
Transverse relaxation, I39
Twisting, 57
UV and visible spectrosCOP.Y· 7, 8, 9
Van der Waals deshielding, !51
Vibrational frequencies, calculation of, 61
Vicinal coupling, 166
Wagging, 57
Wavelength, I
Wavenumber, I
Woodward-Fieser rules
for a,ß-unsaturated carbonyl
compounds, 27
for dienes and trienes, 20
exceptions to, 25
Zero-point energy, 113