Secondary Hydrogen Isotopes Effects. VI . Acetolysis Rate of Cyclopentyl-3,3,4,4-d4 Tosylate

The synthesis 6f cyclopentyl-3,3,4,4-d4 p-toluenesulfonate is described. The acetolysis rate constant of this compound at 50.00 was determined. With the help of the IBM 7090 computer a kinetic isotope effect (kH/kD) of about 0.95 was found to occur. This small rate increase is interpreted as possibly due to the + I effect of d euterium

Secondary Hydrogen Isotopes Effects. VI . Acetolysis Rate of Cyclopentyl-3,3,4,4-d4 Tosylate

The synthesis 6f cyclopentyl-3,3,4,4-d4 p-toluenesulfonate is described. The acetolysis rate constant of this compound at 50.00 was determined. With the help of the IBM 7090 computer a kinetic isotope effect (kH/kD) of about 0.95 was found to occur. This small rate increase is interpreted as possibly due to the + I effect of d euterium

Secondary Hydrogen Isotopes Effects. V. Internal Rearrangement in the Acetolysis of Deuterium Labeled Cyclopropylmethyl Benzenesulfonates

The acetolysis vs. internal rearrangement products ratio was determined for cyclopropylmethyl, cyclopropylmethyi-1 ,1-dii and -3,3-d2 benzenesulfonate and was found to remain constant within the experimental error. The results confirm that both concurrent reactions proceed through a common intermediate in which the bond between the carbonium ion and the leaving group must be pureiy ionic

Secondary Hydrogen Isotopes Effects. V. Internal Rearrangement in the Acetolysis of Deuterium Labeled Cyclopropylmethyl Benzenesulfonates

The acetolysis vs. internal rearrangement products ratio was determined for cyclopropylmethyl, cyclopropylmethyi-1 ,1-dii and -3,3-d2 benzenesulfonate and was found to remain constant within the experimental error. The results confirm that both concurrent reactions proceed through a common intermediate in which the bond between the carbonium ion and the leaving group must be pureiy ionic

A Comparison of Carbon-Carbon Double Bond and Cyclopropane as Neighboring Groups. Solvolysis Rates of 1-Aryl-4-cyclopropylbutyl Chlorides

1-Phenyl-4-cyclopropylbutyl chloride 13a and 1-m-bromophenyl- 4-cyclopropylbutyl chloride 13b were prepared and their solvolysis rates measured. As with corresponding 1-aryl-5-hexenyl chlorides 9, no reaction rate increases were observed. In contrast, 1-aryl-5-methyl-5-hexenyl chlorides 10 and 1-aryl-5-heptenyl chlorides 11 which are isomeric to 13 solvolyze with significant anchimeric assistance of the methyl-substituted aliphatic double bond. This failure of the cyclopropane ring to act as a neighboring group is rationalized in terms of possible charge delocalization in the reaction transition state arising from 13 and from 10 or 11

Deuterium Scrambling During Stereochemical Equilibration of endo- and exo-Norbornanol-3,3-d2

Herewith we wish report about an interesting case of deuterium scrambling during the attempted preparation of exo-norbornanol-3,3-d2 from the endoisomer through equilibration with the aid of fluorenone

Tritium Distribution in 4-0ctene· Prepared by Catalytic Hydrogenation

In orur work on hydrogen isotope effects we needed a symmetrical olefin specifically labeled on the d61Uble bond wi,th tI\u27itium. The simplest way to achieve this seemed to be the preparatiion of an acetylene and the subsequent catalytic reduction with tritium gas to the corresponding olefin. 4-0ctyne was therefore prepaired from n-propyl bromide and d:irsodium acetylide in liquid ammonia by a procedure which was found to· be more practical than the published 101I1es1• 2• 4-0cty.ne was then ireduced wirthout solvent in the presence of Lindlarr catalyst Wlith tritium gas which was produced by ele~trolysis of tritilated sulfuriic acid. The distilled product was pure 4--0eterne as shown by vaipor phase chromatography

5-Methoxyl Participation in Solvolysis and Secondary Deuterium Isotope Effects

Specifically deuterated 4-methoxy-1-pentyl broij\u27ylates (IP- 1,1-d2, IP-2,2-d2) and 5-methoxy-2-pentyl brosylates (IS-2-d, 1S- -1 ,1,1 - d3, 1S-OCD3) were prepared, their solvolysis rates measured in 950/o ethanol and the corresponding kinetic secondary deuterium isotope effects calculated. It was found that the a-effects are strongly reduced in magnitude, which is in contrast with results obtained with several compounds solvolyzing via n- or CJ-participation. The effect found with IP-l,1-d2 (kHfkD = 0.96) is significantly different from the one measured with IS-2-d (kHfkD = 1.06). This difference in the magnitude of the effects must reflect a relatively small difference in the structures of the two transition states, since both IP and IS solvolyze via the same intermediate 2. It is concluded that the magnitude of the u- effP.ct is a sensitive measure of the amount of bridging only if the new bond is already quite strong in the transition state. B-Deuterated brosylates give small effects which differ in magnitude (kH/kD = 0.96 with IP-2,2-d2 and 1.08 with IS-1,1,1-da) corroborating the conclusion that the new C-0 bond is strong in the transition state of both reactions but stronger with IP than with IS. Results obtained in this work are in accord with the earlier conclusion that reduced B-effects in solvolysis of exo-2-norbornyl, 3-cholesteryl, cyclobutyl and 1-methylcyclobutyl derivatives are due to bridging. The inverse isotope effect obtained with IS-OCD3 (kH/kD=0.95) is »inductive« in origin and indicates that the methoxy oxygen bears a considerable amount of positive charge in the reaction transition state

Reactions of Cyclopropylmethyl Benzenesulfonate. Energies and Entropies of Activation

The solvolyses of cyclopropylmethyl derivatives are accelerated and seem to proceed through the formation of non-cla1ssical carbornium i\u27Onsn. These reacti•ons are a•ls:o very often accompa1111ied by extensive rearrangements6 • Thus, the acetolysis of cyc1opropylmethyl benzenesulfonate proceeds simultaneously w;ith a competitive internal rearrangement to products which are 250 times less reactive than the starting materiaF. In the course of our investigation o[ the mecha111ism of these two closely related reactions, we w&nted to gain some information aibout the. corresponiling free energies and entropies of activation

Secondary Hydrogen Isotopes Effects. III. Acetolysis of endoand exo-Norbornyl-5,6-d2 p-Bromobenzenesulfonates

The synthesis of endo- and exo-norbornyl-5,6-d2 p-br omobenzenesulfonates is d escribed. The rate constants of the acetolysis were measured a nd an isotope effect was obser v ed in the rea ction of the exo-isomer. This result is in agreement with the mechanism proposed by Roberts and indicates that the 1,3-hydride shift o ccurs in the rate determining step