Cyclopentane deuteration

That propane is indeed formed by H2 reaction is known by observing the distribution of yields of various isotopic compositions of propane from the radiolysis of an equimolar mixture of cyclopentane and deuterated cyclopentane. Further evidence is provided by the facts that (1) propane is not formed by photolysis below the ionization threshold, and (2) an electric field has no effect on the yield. 

Earlier work on the exchange of methylcyclopentane and methylcyclo-hexane over nickel catalysts at 150°-200° had not shown any discontinuities in the distribution pattern of the products (S9). There was a uniform rise up to a maximum for the fully deuterated species. This is not surprising, since similar behavior was noted with cyclopentane and cyclohexane under the same conditions. At these high temperatures the interchange reaction occurs sufficiently readily to mask any division of the hydrogen atoms into sets. 

In a series of papers, studies have been reported of the exchange of deuterium in, and the deuteration of, benzene (707,40), the exchange of deuterium in cyclopentane (62), and the reactivity of hexane (60) and methylcyclo-pentane (700) over nickel and Ni-Cu alloys. 

A metastable peak for the loss of H from [(CH3)3CH]f has been reported, whereas no loss of D (or H ) could be seen with [(CH3)3CD]t [59]. By taking the instrument s detection limit as an upper level for the missing metastable peak s abundance, the intermolecular isotope effect on the ion abundances has been given as > 1000. Again, the figure provides no reliable information about the kinetic isotope effect. A metastable peak could not be observed for loss of D" from (CD3CD2CD2CH3)t and the intramolecular isotope effect, 7H //D, has been given as at least 240 [778]. Disappearance of metastable peaks on deuteration has also been reported with cyclopentane [639] and cyclopentanone [638]. 

Few studies have been made of the hydrogenation characteristics of these classes of molecule. The deuteration of cyclopentadiene 52) occurred very rapidly at — 34° at the surface of an iron film cyclopen-tene was probably produced as an intermediate but full deuteration to cyclopentane was the only measurable process. A film sintered for 16 min at 200° was active for diene exchange at 90° and yielded product containing one deuterium atom, but it was not active for the addition reaction. 

According to the activation volume data the Diels-Alder dimerization of 1,3-butadiene [39] and o-quinodimethane (Table 2.5, entries (3) and (4), respectively) fall into the same class of concerted processes as those discussed for 1 and 7, while the Diels-Alder dimerization of hexamethylbis(methylene)cyclopentane seems to occur in stepwise fashion. According to the activation volume data summarized in Table 2.6 only the Diels-Alder reaction of 1,3-butadiene with a-acetoxyacrylonitrile seems to proceed concertedly while all other Diels-Alder and homo-Diels-Alder adducts are probably formed in stepwise processes comparable to the corresponding competitive [2 + 2] cycloadditions. Stereochemical investigations of the chloroprene and 1,3-butadiene dimerization using specifically deuterated derivatives confirm the conclusions drawn from activation volume data. In the dimerization of ( )-l-deuteriochloroprene (17) the diastereomeric Diels-Alder adducts ISa-Dz and... 

As distinct from the above-mentioned authors, we explain it by the flat arrangement of the ring on the surface and its exchanging with the surface atoms of deuterium. Then the ring turns over and deuteration takes place on the other side of its plane. For cyclohexane such an arrangement is close to the sextet model (see Fig. 17), and for cyclopentane, to the deformed sextet type (Fig. 20). If this interpretation is... 

Significance of Nonthermal Reactivities. Indistinguishable (Y — t) results have been obtained for protiated and deuterated isotopic cyclopentanes and Cg-Cs alkanes. These comparisons were carried out to suppress the importance of (nR/o- ARj ratio variations, so that sensitive measurement reproducibility and zero-point energy reactivity correlation tests could be accomplished. From the statistical quality of correlation... 

Interest in the cyclopentane 1,3-biradical stems not only from its ease of formation from bicyclo[2.1.0]pentane, but also its formation from 2,3-diazabicyclo[2.2.1]hept-2-ene by either thermolysis or photolysis. Remarkably, the gas phase thermolysis of xo-deuterated material gave mostly inverted bicyclo[2.1.0]pentane (Scheme 6.24). ... 

Experiments with deuterated cyclopentane and C-labeled cyclopentane yield results that are consistent with this interpretation. From fast heteronuclear single quantum coherence (FHSQC) experiments, the chemical shift of the carbon interacting with the metal could also be determined. FHSQC is a 2D NMR technique that can be used to determine the chemical shift of a heteronucleus, in this case C, from the known chemical shift of protons connected to that nucleus. 

---