Reactions of Recoil ³⁸Cl Atoms with Liquid Chlorotoluenes

Abstract

Recoil chlorine ¡Chlorotoluenes /Hot atom chemistry /Ipso attack AbstractThe chemical reactions of recoil 38 C1 atoms have been studied in liquid ortho, meta and para chlorotoluenes and in a 1 :1:1 mixture. In the pure liquids, the total organic yield is less in meta isomer compared to ortho and para isomers and is mainly due to a lower 3 * Cl-for-Cl substitution yield. In systems scavenged with 2 mol % I,, these substitution yields are about same for each of the three isomers. In a 1 :1 :1 mixture of the o : m : ρ isomers, containing 2 mol % I 2 , the ratios of the (hot) 38 Cl-for-Cl substitution yields are close to statistical. The distribution for thermal exchange reactions is however, selective. The 3, Cl-for-H substitution yield is less than 1 % per Η atom-aromatic and methylic-and is scavenger independent. The 3, Cl-for-CH 3 substitution yield is also about 1 %, whereas in a 1 :1 :1 mixture the o : m ; ρ ratio is not far from statistical.

Recoil 38CI Reactions with Halobenzenes: Substituent Effects

“…The increase in the parent yields when the samples are exposed to higher doses has also been reported previously for the substituted chlorobenzenes [4]. This increase was attributed to the radiation-induced thermal ipso substitution reactions, the reported limiting dose being about 500 Gy [ 11 ].…”

“…BHAVE etal. [4] have also reported similar results with o-chlorotoluene at high accompanying 7-doses.…”

“…Our work with mono-and dichlorotoluenes [3,4] has shown that the yields of 38 Cl-for-Cl substitution via thermal ipso attack are lower than in the corresponding chlorobenzenes due to the presence of the CH 3 group. The results for 38 CI atoms with α-chlorotoluenes and their substituted derivatives in the presence of I 2 are contrary to the normal behaviour observed with other arenes [3 b] as both the total organic and parent yields in C 6 H 5 CH 2 C1, C 6 H 5 CHC1 2 and C 6 H S CC1 3 were enhanced by the addition of I 2 , which was explained on the basis of nucleophilic substitution of intermediate benzyliodides by thermal 38 CI" ions.…”

“…Intermolecular competition experiments were performed in order to understand the mechanism and selectivity effects for hot and thermal substitution reactions. To gain more information on these aspects, we chose chlorotoluenes and some substituted derivatives as typical systems [3,4] whilst equimolar mixtures of substituted chlorobenzenes were used by others [5 -7].…”

“…These findings clearly demonstrated that the presence of a second chlorine at different positions in an aromatic compound plays a prominent role in the substitution processes. BRINKMAN and coworkers have found that in 1 : 1 : 1 mixtures of isomeric dichlorobenzenes [5] and in the respective chlorotoluenes [4], the ο: m : ρ substitution yields were almost statistical, whereas the distribution for thermal exchange was very selective, favouring the o-and p-isomers. They have recently extended their studies to different mixtures of isomeric C 6 H 4 C1X (X = F, CI, CH 3 , CF 3 ) compounds to obtain more information on aspects such as relative rates and selectivity for exchange [8].…”