3997-89-5Relevant academic research and scientific papers
Pseudorotation in Cyclopentane. An Experimental Determination of the Puckering Amplitude by NMR in Oriented Solvents
Poupko, R.,Luz, Z.,Zimmermann, H.
, p. 5307 - 5314 (1982)
Proton NMR spectra of normal cyclopentane, 1,2,2',5,5'-pentadeuteriocyclopentane, and randomly deuterated cyclopentane in liquid crystalline solvents between -30 and +110 deg C are reported.The spectra yield all possible distinct average dipolar interactions between the protons in the molecule.These results are compared with the predictions of fife different theoretical models for the dynamic puckering deformation of cyclopentane.Although the general trend in these models is consistent with the experimental results, there is no exact agreemnt between the average dipolar interactions calculated from these models and those obtained experimentally.The experimental results are then subjected to a best-fit analysis in terms of Pitzer's pseudorotation model, using the modification of Adams et al., with the puckering amplitude, q, as a single adjustable parameter.A perfect agreement between the experimental dipolar parameters and those calculated from this model is obtained with q = 0.463 Angstroem.
The Unorthodox Loss of Propyl from the Molecular Ions of Methoxycyclohexane
Molenaar-Langeveld, Tineke A.,Nibbering, Nico M. M.
, p. 426 - 432 (1983)
It is shown by field ionization kinetics, D and 13C labelling and metastable ion studies that the loss of a propyl radical from the molecular ion of methoxycyclohexane occurs via two routes.At a molecular ion lifetime of -10 s propyl is eliminated in the 'classic' way, i.e. by successive cleavage of the C(1)-C(2) bond, 1,5-H shift from C(6) to C(2) and cleavage of the C(4)-C(5) bond.At 10-10 s the other pathway for propyl loss starts to take place, which is initiated by a hydrogen shift from position 3 or 5 to the methoxy group.This leads in a series of steps to the formation of the 3-methoxyhexene-1 ion, which eventually eliminates a propyl radical.In some of the steps specific hydrogen-deuterium exchange processes have been observed.
Jet-cooled fluorescence excitation spectra, conformation, and carbonyl wagging potential energy function of cyclopentanone and its deuterated isotopomers in the S1(n, ?*) electronic excited states
Zhang, Jian,Chiang, Whe-Yi,Laane, Jaan
, p. 6129 - 6137 (1993)
The jet-cooled fluorescence excitation spectra of cyclopentanone and its 2,2,5,5-d4 isotopomer have been recorded in the 305-335 nm region.In addition, the spectra of d1, d2, and d3 species were obtained from isotopic mixtures.The electronic band origin of the d0 molecule for the S1 (n, ?*) state of A2 symmetry occurs at 30 276 cm-1, while that of the d4 molecule is at 30 265 cm-1.More than 100 fluorescence bands were assigned for each species.These arise from combinations of ν3 (C=O stretch), ν11 (ring-angle bending), ν18 (ring twisting), ν25 (C=O out-of-plane wag), ν26 (ring bending), and ν36 (C=O in-plane wag) and their vibrational excited states.The vibrational frequencies for ν3, ν11, and ν36 are significantly lower in the S1 state than the S0 ground state.However, the out-of-plane ring modes ν18 and ν26 are only slightly shifted.A progression observed for ν26 does indicate that in the S1 state, the bent ring conformation lies about 500 cm-1 above the ring-twisting minimum and corresponds to a saddle point in the two-dimensional ring-twisting/ring-bending potential energy surface.Band progressions for ν18 can be used to calculate the ring-twisting barriers (the barriers to planarity) for the d0 and d4 isotopomers to be 1433 and 1240 cm-1, respectively.Because of limited data, however, these values may be as much as several hundred cm-1 too high.The energies for the C=O out-of-plane wagging states up to v25 = 9 for each isotopomer were determined for the S1 state and these were used to calculate the C=O wagging potential energy functions for each.In the S1 state, the barrier to inversion of the C=O group is 672+/-10 cm-1 and the wagging angle is 22 deg +/- 1 deg.
Au-Catalyzed Pentannulation Reaction of Propargylic Esters Occurring at C(sp3)-H Site
Shiroodi, Kazem Roohollah,Sugawara, Masumi,Ratushnyy, Maxim,Yarbrough, Douglas C.,Wink, Donald J.,Gevorgyan, Vladimir
supporting information, p. 4062 - 4065 (2015/09/01)
A gold-catalyzed cascade cyclization reaction of easily accessible propargylic esters to cyclopentenones has been developed. This transformation features an unprecedented pentannulation reaction of propargylic esters which occurs at an unactivated C(sp3)-H site to efficiently produce functionalized mono-, bis-, and tricyclic cyclopentenones.
Solvolytic studies in cycloalkyl systems
Ranganayakulu,Murthy
experimental part, p. 307 - 313 (2012/04/04)
The angular dependence of the C-H/C-D bond for a stabilization of the developing carbonium ion in the transition state of the solvolysis reaction of cycloalkyl halides has been investigated. This has been achieved by studying the rate of solvolysis of eight cyclic β-deuterated 1-alkyl-1-chloro cycloalkanes. Reaction rates for the solvolysis of both β-C-H and of the corresponding β-C-D compounds have been determined and the difference in the rate ratio i.e. kH/kD was attributed to the differential hyperconjugative effects exerted by β-hydrogens in different ring systems. By varying the ring size from C5 to C12 the dihedral angle of C-H bond in relation to the vacant "p" orbital on the trigonal carbon, (carbonium ion transition state) changes leading to changes in hyperconjugative stabilization of the intermediate carbonium ion with a consequent change in the rate of solvolysis. β-Deuterium isotope effects thus obtained for different cyclic systems were related with the actual bond angles between β-C-H bonds and the developing carbonium ions. Using the Allinger's force field calculations the best geometry for both the carbonium ions and the starting halo hydrocarbons were calculated.
Michael addition-elimination mechanism for nucleophilic substitution reaction of cycloalkenyl iodonium salts and selectivity of 1,2-hydrogen shift in cycloalkylidene intermediate
Fujita, Morifumi,Wan, Hyeok Kim,Fujiwara, Koji,Okuyama, Tadashi
, p. 480 - 488 (2007/10/03)
(Chemical Equation Presented) Reactions of cyclohexenyl and cyclopentenyl iodonium salts with cyanide ion in chloroform give cyanide substitution products of allylic and vinylic forms. Deuterium-labeling experiments show that the allylic product is formed via the Michael addition of cyanide to the vinylic iodonium salt, followed by elimination of the iodonio group and 1,2-hydrogen shift in the 2-cyanocycloalkylidene intermediate. The hydrogen shift preferentially occurs from the methylene rather than the methine β-position of the carbene, and the selectivity is rationalized by the DFT calculations. The Michael reaction was also observed in the reaction of cyclopentenyliodonium salt with acetate ion in chloroform. The vinylic substitution products are ascribed to the ligand-coupling (via λ3-iodane) and elimination-addition (via cyclohexyne) pathways.
Strong experimental evidence of C-H...O hydrogen bonds in cyclopentanone: The splitting of the v(C=O) mode revisited
Vaz, Pedro D.,Ribeiro-Claro, Paulo J.A.
, p. 6301 - 6305 (2007/10/03)
The splitting of the ν(C=O) mode in cyclopentanone was investigated through an extensive vibrational study. Temperature and solvent variation study, isotopic substitution, and ab initio calculations of monomer and dimer structures and spectra were also studied. The results showed that the splitting of the ν(C=O) mode to Fermi resonance was based on several of erroneous observations.
Classical Organic Reactions in Pure Superheated Water
Kuhlmann, Barbara,Arnett, Edward M.,Siskin, Michael
, p. 3098 - 3101 (2007/10/02)
At high temperatures and pressures, pure liquid water becomes a surprisingly effective medium for the reactions of organic compounds.It may function simultaneously as a convenient solvent, catalyst, and reagent for reactions which are typically acid- or base-catalyzed.Rapid and highly selective conversion are observed for the majority of the compounds in this study.
Pseudorotation of Cyclopentane and Its Deuteriated Derivatives
Bauman, L. E.,Laane, J.
, p. 1040 - 1051 (2007/10/02)
The gas-phase mid-infrared Raman spectra of cyclopentane, cyclopentane-d, cyclopentane-1, 1-d2, cyclopentane-1,1,2,2,3,3-d6, and cyclopentane-d10 have been recorded and analyzed in order to investigate the vibrational potential energy surface associated w
Isomerization and Fragmentation of Methylfuran Ions and Pyran Ions in the Gas Phase
Spilker, Ruediger,Gruetzmacher, H.-F.
, p. 459 - 466 (2007/10/02)
The mutual interconversion of the molecular ions +. of 2-methylfuran (1), 3-methylfuran (2) and 4H-pyran (3) before fragmentation to + ions has been studied by collisional activation spectrometry, by deuterium labelling, by the kinetic energy release during the fragmentation, by appearance energies and by a MNDO calculation of the minimum energy reaction path.The electron impact and collisional activation mass spectra show clearly that the molecular ions of 1-3 do not equilibrate prior to fragmentation, but that mostly pyrylium ions + arise by the loss of a H atom.This implies an irreversible isomerization of methylfuran ions 1 and 2 into pyran ions before fragmentation, in contrast to the isomerization of the related systems toluene ions/cycloheptatriene ions.Complete H/D scrambling is observed in deuterated methylfuran ions prior to the H/D loss that is associated with an isotope effect kH/kD=1.67-2.16 for metastable ions.In contrast, no H/D scrambling has been observed in deuterated 4H-pyran ions.However, the loss of a H atom from all metastable +. ions gives rise to a flat-topped peak in the mass-analysed ion kinetic energy spectrum and a kinetic energy release (T50) of 26+/-1.5 kJ mol-1.The MNDO calculation of the minimum energy reaction path reveals that methylfuran ions 1+. and 2+. favour a rearrangement into pyran ions before fragmentation into furfuryl ions, but that the energy barrier of the first rearrangement step is at least of the same height as the barrier for the dissociation of pyran ions into pyrylium ions.This agrees with the experimental results.
