Nature of the carbonium ion. VIII. Cycloalkyl cations from thiocyanate isomerizations

Abstract

Thermal isomerizations of cyclopropylcarbinyl (1), cyclobutyl (2), cyclopentyl (4), and cyclooctyl (5) thiocyanates were effected in sulfolane and, where appropriate, less polar aprotic solvents. In these cases, formation of isomeric isothiocyanates at relative rates which paralleled the relative rate order observed for acetolyses of the corresponding p-toluenesulfonate esters indicated the intermediacy of cycloalkyl cations. The cyclobutyl related compounds, 1 and 2, isomerized to similar product mixtures but at vastly different rates. The product ratios observed in these cases did not resemble those from solvolyses of the analogous arylsulfonate esters, thereby suggesting that the partition of the intermediate ion(s) is governed largely by the proximity of the counterion in the intermediate ion pairs. Studies of the isomerizations of 1 with ionic and Lewis acid catalysts supported this notion. The larger cycloalkyl thiocyanates 4 and 5 isomerized only to their corresponding skeletally unrearranged isothiocyanate isomers 9 and 10, respectively. Reaction rates were in keeping with the relative driving forces to ionization for these secondary thiocyanates. Interpretations of the results are presented involving ion pair intermediates in which counterion position is largely influential in determining product compositions.

N-Cyano-N,N,N-trialkylammonium salts. Synthesis and reactions

“…(3), 223 (21), 205 (11), 204 (100), 203 (22), 202 (4), 183 (5), 154 (17), 152 (5), 127 (23), 77 (24), 51 (12).…”

“…Caled for CeHi0N2 (110.16): C, 65.41; , 9.15; N, 25.44. Found: C, 65.45; H, 9.25; N, 25.00. 5-Hydroxypentyl-n-propylcyanamide was characterized as follows: bp 140°( 0.65 mm); ir (thin film) 2203 cm™1 (strong, CN); nmr (CDCls) 0.97 (t, CH3, 3 ), 1.40-1.90 (m, CH2, 8 ) 2.90-3.40 (m, CH4, 4 H), and 3.60 (t, CH2, 2 H); mass spectrum m/e (rel abundance) 170 (M+, 4), 155 (15), 142 (4), 141 (10), 128 (19), 127 (8), 126 (5), 125 (10), 123 (6), 114 (16), 113 (6), 112 (7), 111 (10), 110 (4), 105 (8), 100 (11), 99 (9), 98 (22), 97 (35), 88 (6), 96 (8), 88 (5), 86 (6), 85 (51), 84 (7), 83 (13), 82 (7), 81 (43), 80 (15), 79 (8), 77 (17), 75 (39), 72 (22), 71 (5), 70 (25), 69 (48), 58 (8), 57 (21), 56 (14), 55 (100), 54 (16), 53 (11), 51 (7), 45 (6), 44 (18), 43 (68), 42 (22), 41 (85), 39 (28).…”