ensure the dryness. The solvent-electrolyte solution was passed into the cell through a column of activated neutral alumina (grade 1) immediately before the measurements were made16.
Tetrabutylammonium hexaflorophosphate was recrystallised from ethyl acetate. The recrystallised product was then dried in a vacuum desiccator.
Oxalates
Diethyl oxalate (1a). (Aldrich) Was washed three times with sodium bicarbonate, once with distilled water and then dried in magnesium sulphate. The solvent was evaporated off and the product was distilled off (185°C). The distilled diethyl oxalate was then dried over anhydrous sodium carbonate before use.
Ethyl benzyl oxalate (2a)2. Ethyl oxalyl chloride (1.36 ml, 0.012 mole) was added slowly at room temperature to a dry ether (50 ml) solution of the benzyl alcohol (1.26 ml, 0.012 mole) and pyridine (0.99 ml, 0.012 mole). This mixture was refluxed for 12 hours under nitrogen. The precipitate of pyridinium hydrochloride was filtered off and the organic layer washed with sodium bicarbonate (NaHCO3) and then dried over MgSO4. The solvent was evaporated to give an oily product (1.78g, 70%); 1H NMR dH (270 MHz, CDCl3): 7.3 (5H, m, Ar-H), 5.2 (2H, s, CH2), 4.35 (2H, q, J = 5.5Hz, CH2) and 1.4 (3H, t, J = 5.5Hz, CH3); 13C NMR dC (62.5 MHz, CDCl3): 155.9, 140.9, 128.7, 127.4, 71.6, 58.9 and 13.3.
Dibenzyl oxalate (1b)17. Was prepared from oxalyl chloride and two equivalents of benzyl alcohol according to the above procedure. The product was obtained as a white solid (46%); m.p. 57-60°C (lit.ref 58-60°C); 1H NMR dH (270 MHz, CDCl3): 7.45-7.30 (10H, m, Ar-H) and 5.2 (4H, s, CH2); 13C NMR dC (62.5 MHz, CDCl3): 155.9, 140.9, 128.7, 127.4, 127.0 and 71.6.
Ethyl 4-methyl benzyl oxalate (2b). Was prepared by the above procedure from ethyloxalyl chloride and 4-methylbenzyl alcohol to give white solid (76%); C12H14O4 requires: C, 64.85; H, 6.35; O, 28.80 %. Found: C, 63.84; H, 6.47; O, 28.72 %); 1H NMR dH (270 MHz, CDCl3): 7.35 (2H, d, J = 12Hz, Ar-H), 6.9 (2H, d, J = 12Hz, Ar-H), 5.2 (2H, s, CH2), 4.35 (2H, q, J = 7.4Hz, CH2), 3.8 (3H, s, CH3), and 1.35 (3H, t, J = 7.4Hz, CH3); 13C NMR dC (62.5 MHz, CDCl3) : 155.9, 137.9, 136.6, 129.4, 127.2, 71.6, 58.9, 20.9 and 13.3.
Ethyl 4-methoxybenzyl oxalate (2c). Was prepared by the above procedure from ethyloxalyl chloride and 4-methoxybenzyl alcohol to give white solid (76%); C12H14O5 requires: C, 60.50; H, 5.92; O, 33.58 %. Found: C, 60.44; H, 5.72; O, 34.72 %); m.p. 40-43°C; 1H NMR dH (270 MHz, CDCl3): 7.35 (2H, d, J = 12Hz, Ar-H), 6.9 (2H, d, J = 12Hz, Ar-H), 5.2 (2H, s, CH2), 3.8 (3H, s, CH3), 4.35 (2H, q, J = 7.5Hz, CH2) and 1.35 (3H, t, J = 7.5Hz, CH3); 13C NMR dC (62.5 MHz, CDCl3) : 160.9, 155.9, 133.2, 128.3, 114.3, 71.6, 58.9, 56.0 and 13.1.
Ethyl 4-chlorobenzyl oxalate (2d). Was prepared from ethyloxalyl chloride and 4- chlorobenzyl alcohol according to the above procedure and the product was obtained as a white solid (90%); C11H11ClO4 requires: C, 54.45; H, 4.57; O, 26.37 %. Found: C, 54.48; H, 4.72; O, 26.72 %); m.p. 77-79°C; 1H NMR dH (270 MHz, CDCl3): 7.35 (4H, s, Ar-H), 5.25 (2H, s, CH2), 4.35 (2H, q, J = 7.2Hz, CH2) and 1.4 (3H, t, J = 7.2Hz, CH3); 13C NMR dC (62.5 MHz, CDCl3): 155.9, 139.0, 132.7, 129.1, 128.7, 71.6, 58.9 and 13.3.
