17 research outputs found
B-Deuterium Isotope Effect in Solvolysis of 1 ,2-Dimethyl-exo-2- -norhornyl p-Nitrohenzoate
Secondary (:-deuterium isotope effects have been shown to be remarkably constant with change of solvent1. The ratio, kH/kD, , was 1.22 in solvolysis of 1-phenylethyl chloride in ethanol-water mixtures ranging from 50 vol 0/o to 80 vol O/o of ethanol. It was proposed that the transition state is very nearly the same in all the solvents studied. The yields of styrene (as an elimination product) were between 1 and 3 percent
Secondary Deuterium Isotope Effects in Solvolysis of Cyclopentyl p-Bromobenzenesulfonate in Dioxane-Water Mixtures. Stereochemistry of E1 and SN 1 Reactions
In the continuation of our study1 on the rela:tionship between the magnitude
of secondary deuterium isotope effects and the reaction pathways in
solvolytic SNl and El reaotions, we report the results obtained in differentdioxĀ·ane- water (D- W) mixtures wiĀ·th specifd.cally deuternrted cyclopenrtylbrosylates. For this purpose, required cyclopentainol, cyclopentanol-1-d (a-d),
cis-cyclopentanol-2-d (cis-B-d), trans-cyclopentanol-2-d (trans-B-d) and cyclopentarrol-2,3,5,4-d4 (B-d.;) were prepared as described by Streitwieser et al.2
The correspond~ng b.rosylates were prepared by rthe usual Tipson procedure3 ā¢The deuterium content was greater than 93 0/o 1in all of deuterated compounds
as was determined by mass spectral analysis
Mass Spectra of Labeled Cyclopentanols
The fragmentation of cyclopentanol has been studied by employing
the deuterium labeling technique. Starting from the molecular
ion the following specific processes could be established:
loss of H from the position 1, loss of CH3 formed mainly from 2
(or 5) position after a-scission, loss of H 2 0 as a 1,3-elimination,
and loss of C2H 5 generated from 2 and 3 or 4 and 5 positions plus
one hydrogen from position 5 or 2, respectively. The results are
discussed
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
1,3-Hydrogen Migration in the Solvolysis of 2-(L\u27.1 3-Cyclopentenyl)ethyl p-Toluenesulfonate
2-(Ll 3-Cyclopentenyl)ethyl-1,1-d2 tosylate was prepared and
solvolyzed in 80 per cent aqueous acetic acid. Conversion of the
so1volysis products to exo-2-norbornanol and integration o-f the peak
areas of its n.m.r. spectrum indicates 10-15 per cent of 1,3-deuterium
migration. The hypothesis is advanced that this migration
must have taken place after the rate determining step of the solvolysis.
exo-2-Norbornanol-d2 resulting from this reaction was converted
to the corresponding p-bromobenzenesulfonate and solvolyzed
in acetic acid. Possible explanations for the observed
secondary isotope effect (kH/kD 1.13) are given
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 reactiā¢ons are aā¢ls:o very often accompa1111ied by extensive rearrangements6 ā¢ 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
Mass Spectra of Bicyclo[2.2.1 ]-2-heptanols
The fragmentation of bicyclo[2.2.1]-2-heptanol, endo- (I) and
exo- (Ia), 1-methylbicyclo[2.2.1]-2-heptanol, endo- (II) and exo(
IIa) and 2-methylbicyclo[2.2.1]-2-heptanol, endo- (III) has been
studied by employing the deuterium labelling technique. The
results obtained indicate Ā· that the existence of nonclassical carbonium
ion is of no significant importance during the fragmentation
of the molecular ion of these alcohols and that the
dehydration of the molecular ion is stereospecific regarding the
position of eliminated hydrogen