Conformational analysis of 5,5-bis(halomethyl)-1,3-dioxanes

Investigation of stationary points on the potential energy surface of a number of 5,5-bis(halomethyl)-1,3-dioxanes using DFT-approximation of PBE/3ζ revealed the only path of chair form interconversion proceeding through an intermediate minimum corresponding to a 2,5-twist-conformer.     

Ring inversion in 5,5-disubstituted 1,3-dioxanes

The conformational mobility was studied by dynamic PMR and the free energies of activation of the conformational transitions of 5,5-bis(chloromethyl)-, 5,5-bis(iodomethyl)- and 2,3-pentamethylene-bis-5,5-bis(chloromethyl)-1,3-dioxanes were determined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 607–608, May, 1987.     

Electron impact mass spectrometry of 2,5-bis(p-R-phenyl)thiophenes

The mass spectra of a series of 2,5-bis(p-R-phenyl)thiophenes are reported and discussed. The fragmentation patterns and mechanisms postulated have been confirmed by the determination of the metastable peaks. All the compounds possess the molecular ion as the base peak.     

Conformation of 5,5-disubstituted 2,2-dimethyl-1,3-dioxanes

It was established by PMR spectral data that in solutions of derivatives of 5-acetoxymethyl-, 5-methyl-, and 5-hydroxymethyl-2,2-dimethyl-1,3-dioxanes with nitrogen-containing substituents (2,4-disubstituted 1,3,5-triazin-6-ylamino, benzamido, and nitro groups) with an N-C₍₅₎ bond the 1,3-dioxane ring exists in the chair conformation with primarily an axial orientation of the nitrogen-containing substituent. Depending on the nature of the substituents attached to the C₍₅₎ atom, the 1,3-dioxane ring may exist either in the stable chair conformation or may undergo rapid inversion of the chair-chair type at 20 °C.The author sincerely thanks A. I. Kol'tsov for his assistance in recording and interpreting the PMR spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 468–473, April, 1985.     

Electron impact mass spectra of 1-methyl-3-(2-benzothiazolylhydrazono)-2-indolinones

A study of the fragmentation of l-methyl-3-(2-benzothiazolylhydrazono)-2-indolinones on electron impact reveals that the major processes involve N? N bond fission and the competing loss of CO from the molecular ion.     

Electron impact mass spectra of 2-hydrazono-1,3-thiazolidin-4-one derivatives

Mass fragmentation of 2-hydrazono-1,3-thiazolidin-4-ones is dominated by two processes, namely cleavage of the hydrazone fragment with accompanying proton transfer from the latter to the thiazolidine ring, and cleavage of a hydrazone imide residue.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1117–1119, August, 1990.     

Electron impact mass spectra of 2-[acyl(alkyl)amino]oxazoles

The mass spectral behaviour of 2-methyl-N-butyl-N-(4-methyloxazol-2-yl)propanamide is characterized by cleavage of the acylamino substituents and the elimination of a hydroxyl radical. An understanding of this elimination has been obtained from the analysis of further 2-[acyl(alkyl)amino]oxazoles and the use of deuterium labelled compounds.     

Electron impact mass spectra of meliacins

The electron impact mass spectra of some new meliacins and their derivatives are discussed. The major fragmentation modes include the functional group losses, the different ring cleavages and the loss of the furan residue as neutral fragments. A mechanism for the loss of the furan moiety from the molecular ion is discussed in detail with the help of deuterium labelling, high resolution and metastable data.     

Electron impact mass spectrometry of 2-(methoxycarbonylmethyl)-2-phenyl-1,3-benzoxathiole and 2-acetonyl-2-phenyl-1,3-benzoxathiole

The electron impact mass spectrometric behaviour of 2-(methoxycarbonylmethyl)-2-phenyl-1,3-benzoxa-thiole 3a and 2-acetonyl-2-phenyl-1,3-benzoxathiole 3b has been studied in detail. The structures of the more interesting fragment ions have been confirmed with the aid of accurate mass measurements, linked scans and collisional activation experiments. In addition to the ionic species already described in the general fragmentation pattern of 1,3-benzoxathiole derivatives, other fragments arising from the interaction of the carboxy-containing chain with the sulfur atom of these compounds have been observed and evidence presented.     

Electron impact studies—LXVII. The mass spectra of alkyl-1,3-dithianes

The mass spectra of 1,3-dithiane, 2-methyl- and 2,2-dimethyl-1,3-dithiane have been studied by ²H labelling and metastable defocusing. The various molecular ions eliminate S₂H. to produce the ions [C₄H₇]⁺, [C₅H₉]⁺ and [C₆H₁₁]⁺ respectively, each of which scramble the hydrogens either before or accompanying further decomposition. Other processes are complex, but parallel those already reported for 2-aryl-1,3-dithianes.     

Synthesis of 5,5-bis(difluoroamino)-2-hexanone

Conclusions A method was developed for the preparation of 5,5-bis(difluoroamino)-2-hexanone by the acid hydrolysis of the sodium salt of 2-nitro-5,5-bis(difluoroamino)hexane.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2145–2146, September, 1973.     

Electron impact mass spectra of some enamines

The mass spectra of α,β-diarylaminocrotonic acid anilides have been determined and the fragmentation pathways are now discussed. The proposed pathways have been confirmed by deuterium labelling, the spectrum of the model compound, or the appropriate metastables. The detailed electron impact data are given.