Reactions of 1‐bromo‐2‐phenylethane and aluminium bromide: Part I. Isomerisation of 1‐bromo‐2‐phenylethane‐1‐¹⁴C

Abstract

The kinetics of the reaction involving the isomerisation of I -bromo-2-phenylethane-1-"T into 1-bromo-2-phenylethane-2-14C under the influence of aluminium bromide in carbon disulphide has been studied in the temperature range of -70" t o -100". The energy of activation is 9.8 kcals/mole.The kinetic results can be explained if nearly all aluminium bromide is assumed to be bound as the complex CgH& : AIBr3. The reaction of CgHsBr : AIBr3 with one of the ions formed in the ionisation of the complex C~H D B~. A l~B r s is represented as the rate determining step of the isomerisation reaction.

The kinetics of the aluminium bromide catalyzed isomerization of 1-propyl bromide

“…(2) to the experiments also shows that the isomerization at −19 • C depends for about 82% on the reaction of AlBr 4 − with 1-C 3 H 7 Br·AlBr 3 , for 15% with 1-C 3 H 7 Br·Al 2 Br 6 and only for 3% with the 1-C 3 H 7 Br·Al 2 Br 6 clusters. This agrees with the conclusion of the authors where a reaction of the AlBr 4 − ion with the 1-C 3 H 7 Br·AlBr 3 complex is presumed to be in accordance with the results of the isomerization of 1-bromo-2-phenylethane-1 described previously by Adema and Sixma [7].…”

“…The latter is also contained in clusters of two molecules. The following reactions refer to the isomerization step: Reactions k f /k b Complex and cluster formation 1-C 3 H 7 Br + AlBr 3 = 1-C 3 H 7 Br · AlBr 3 (r.2) 1.29 × 10 6 /10 l/mol 1-C 3 H 7 BrAlBr 3 + AlBr 3 = 1-C 3 H 7 Br · Al 2 Br 6 (r. 3) 15000/10 l/mol 2-C 3 H 7 Br + AlBr 3 = 2-C 3 H 7 Br · AlBr 3 (r. 4) 3.4 × 10 6 /10 l/mol 2-C 3 H 7 Br · AlBr 3 + AlBr 3 = 2-C 3 H 7 Br · Al 2 Br 6 (r. 5) 17000/10 l/mol 1-C 3 H 7 Br · Al 2 Br 6 + 1-C 3 H 7 Br · Al 2 Br 6 = [1-C 3 H 7 Br · Al 2 Br 6 ] 2 (r. 6) 1000/10 l/mol 1-C 3 H 7 Br · Al 2 Br 6 + 2-C 3 H 7 Br · Al 2 Br 6 = [1-and2-C 3 H 7 Br · Al 2 Br 6 ] (r. 7) 1500/10 l/mol 2-C 3 H 7 Br · Al 2 Br 6 + 2-C 3 H 7 Br · Al 2 Br 6 = [2-C 3 H 7 Br · Al 2 Br 6 ] 2 (r. 8) 2250/10 l/mol Dissociation Al 2 Br 6 = AlBr 3 + AlBr 3 (r.1) 10/10 11 mol/l 1-C 3 H 7 Br · Al 2 Br 6 = 1-C 3 H 7 Br · AlBr δ+ ·AlBr 4 δ− = 1-C 3 H 7 Br · AlBr 2 + + AlBr 4 − (r.9) 10/10 5 mol/l 2-C 3 H 7 Br · Al 2 Br 6 = 2-C 3 [4] in accordance with the hydrogen isotope effect observed with 2,2-dideutero-1-propyl bromide and 2-deutero-1-propyl bromide [2]. The complex scheme of the isomerization reactions is presented in Table 1.…”