Problems
- The 1H NMR spectrum of, 4,4-dimethyl-2-pentanone, taken at 300 MHz, shows signals at the following positions: 307, 617, and 683 Hz downfield from tetramethylsilane.
(a) What are the chemical shifts (δ) of these signals?
(b) What would their positions be in hertz, relative to tetramethylsilane, if the spectrum were recorded at 90 MHz? At 500 MHz?
(c) Assign each signal to a set of hydrogens in the molecule.
- Predict the structure of the compounds from the data given below.
(a)
Molecular Formula: C4H10O
IR (ν/cm-1): 3339, 2957, 2874, 1471, 1387, 1041
1H NMR (δ): 3.91(s, 1H), 3.35(d, 2H), 1.81 -1.65 (m, 1H), 0.98 (d, 6H)
(b)
Molecular Formula: C5H10O2
IR (ν/cm-1): 2984, 2945, 1740, 1467, 1371, 1347, 1192
1H NMR (δ): 4.24(q, 2H), 2.35(q, 2H), 1.34(t, 3H), 1.16 (t, 3H)
(c)
Molecular Formula: C 8 H 14
IR (ν/cm -1 ): 2963, 2936, 2841, 1484, 1379, 1338, 1278, 1073
1H NMR (δ): 2.14 (t, 2H), 1.50(q, 2H), 0.98 (t, 3H)
(d)
Molecular Formula: C4H9Br
IR (ν/cm-1): 2970, 2922, 2878, 1458, 1379, 1209, 1151
1H NMR (δ): 4.08(m, 1H), 1.87 (q, 2H), 1.70(d, 3H), 1.11( t, 3H)
(e)
Molecular Formula: C11H14O2
IR (ν/cm-1): 2981, 2938, 2874, 1893, 1803, 1510, 1259, 1101
1H NMR (δ): 10.0(s, 1H), 7.87 (d, 2H), 7.01(d, 2H), 1.87(m, 2H), 1.61( m, 2H), 1.01( t, 3H)
(f)
Molecular Formula: C3H6O2
IR (ν/cm-1): 2988, 1716, 1468, 1415, 1240, 1078
1H NMR (δ): 11.5 (broad s, 1H), 2.40(q, 2H), 1.15 (t, 3H)
(g)
Molecular Formula: C8H8O2
IR (ν/cm-1): 2924, 1689, 1589, 1417, 1131
1H NMR (δ): 12.0 ( broad s, 1H), 8.1-7.9 (m, 1H), 7.54-7.23( m, 3H), 2.41 (s, 3H)
- Predict the structures of the following compounds from the data given below.
(a)
Molecular Formula: C9H10O3
Mass (m/z): 166 (90%), 94(100%)
IR (ν/cm-1): 3047, 2637, 2545, 1718, 1433, 1218
1H NMR (δ):10.3(broad s, 1H), 7.15 (t, 2H), 6.82 (t, 1H), 6.78(d, 2H), 4.21 (d, 2H), 2.74(t, 2H)
13C NMR (δ): 177.3, 158.3, 129.2, 121.1, 114.5, 62.8, 34.3
(b)
Molecular Formula: C9H12
Mass (m/z): 120 (50%), 91(100%)
IR (ν/cm-1): 3062, 2865, 1455
1H NMR (δ):7.35(t, 3H), 7.25(d, 2H), 2.74(t, 2H), 1.78-1.65(m, 2H)
13C NMR (δ): 142.6, 128.4, 128.1, 125.5, 38.0, 24.5, 13.8
(c)
Molecular Formula: C6H6NBr
Mass (m/z): 170.98 (100%), 172.96 (97%)
IR (ν/cm-1): 3400, 3100, 2985
1H NMR (δ):7.04(t, 1H), 6.89-6.86(m, 1H), 6.86(m, 1H), 6.61-6.54(m, 1H), 3.0 (broad s)
13C NMR (δ): 130.6, 123.0, 122.0, 121.1, 117.9, 114.0
(d)
Molecular Formula: C8H10O
Mass (m/z): 122.07(100%)
IR (ν/cm-1): 3300, 3100, 3031, 2984, 2900
1H NMR (δ):7.36-7.31 (m, 3H), 7.28-7.25 ( m, 2H), 3.83 (t, 2H), 2.86 (t,2H ), 2.36 (broad s, 1H)
13C NMR (δ):138.7, 129.0, 128.7, 126.2, 63.5, 39.1
(e)
Molecular Formula: C5H8O
Mass (m/z): 55.0(100%), 41.0 (50%)
IR (ν/cm-1): 2967, 2919, 2814, 1749,1409
1H NMR (δ):187-1.78 (m,4H), 1.68-1.55 (m, 4H)
13C NMR (δ): 217.5, 38.1, 23.0
(f)
Molecular Formula: C6H10O
Mass (m/z): 69.0(29%), 55.0(100%), 42.0( 61%)
IR (ν/cm-1): 2935, 2868, 1716
1H NMR (δ): 1.85 (t, 4H), 1.40-1.32(m, 2H), 1.27-1.21(m,2H )
13C NMR (δ): 210.0, 41.2, 27.8, 25.5
(g)
Molecular Formula: C7H9O
Mass (m/z):
IR (ν/cm-1): 3457, 3370, 3048, 2957, 2836, 1614, 1518, 1461
1H NMR (δ):7.11-6.84(m,2H ), 6.94-6.92(d,1H ), 6.86-6.81(m, 1H), 3.97 (broad s, 1H), 3.91(s, 3H)
13C NMR (δ):147.5, 136.8, 124.1, 118.4, 115.2, 110.8, 55.6
Text Books
• P. Y. Bruce and K J R. Prasad, Essential Organic Chemistry , Pearson Education, New Delhi, 2008.
• C. M. Loudon , Organic Chemistry , Oxford University Press, New Delhi, 2002.
• R. R. Morrison, R. N. Boyd and S. K. Bhattacharjee, Organic Chemistry , Dorling Kindersley (India) Pvt. Ltd, New Delhi, 2011.