Radical and Photochemical Reactions of the Nitrosites of Humulene and Caryophyllene

MacAlpine, Derek Kenneth (1977) Radical and Photochemical Reactions of the Nitrosites of Humulene and Caryophyllene. PhD thesis, University of Glasgow.

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Abstract

The Thesis is concerned with the following two main topics; 1) First the reactions of chloroform solutions of humulene (14) and humulene nitrosite (17) with the oxides of nitrogen were investigated. 2) In conjunction with the first topic a study was made of the products obtained when, a) crystalline samples of humulene nitrosite (17) and, b) solutions of humulene nitrosite in the aprotic solvents chloroform, toluene, and benzene, and c) solid solutions of humulene nitrosite in dinitro-humulene (24) are irradiated with red light. The mechanistic flow charts contained in S.1 and S.2 explain the formation of the products observed during these studies. The products obtained were characterised in the manner described below. 1) All derivatives marked with a single asterisk were isolated using chromatographic techniques, obtained where possible in a pure crystalline state, and characterised using a combination of elemental analysis, and 1H n. m. r., 13C n. m. r., infra-red and mass spectroscopy. 2) Derivatives marked with a double asterisk, were isolated as mixtures of similar isomeric compounds which could not be separated by chromatographic or other means. The structures postulated are consistent with the available spectroscopic data. 3) Those nitroxide radicals which were not isolated and character- ised, were detected using e. p. r. spectroscopy, and the spin Hamiltonian parameters were obtained. The photochemical reactions shown in figure S.2, were also monitored in an infrared spectrometer, and the changes observed in the spectra, were shown to be consistent with the structures postulated for the nitroxide radicals. 4) The remaining species shown in figures S. 1 and S. 2 are transient intermediates, which were not detected, but previous workers investigating the chemistry of C-nitroso compounds, and of humulene derivatives, have postulated intermediates of similar structure. Topic one: The reactions of humulene and humulene nitrosite with the oxides of nitrogen Three main products are obtained from the reaction of humulene with the oxides of nitrogen, humulene nitrosite (17), dinitro-humulene (24), and nitro-nitrato-humulene (26), each forming by the addition of the relevant oxides of nitrogen, over the double bond of humulene indicated in figure S. 1. When humulene nitrosite is reacted with N2O3, the initial stages of the reaction involve the addition of two molecules of nitric oxide to the nitroso group of humulene nitrosite, forming the diazonium nitrate complex (37), as shown in figure S.1. This complex subsequently decomposes with the evolution of nitrogen, forming an aliphatic radical (18). By studying the reaction products, this aliphatic radical (18), is deduced to stabalise in the following four ways. 1) The first option is for the radical (18), to add NO2 forming dinitro-humulene (24). 2) Second, an ONO2 radical can abstract a proton, forming the isomeric species (41), (42), and (43). 3) Third, the radical can react with humulene nitrosite, forming nitroxide radical (19). 4) In its final mode of behaviour, (18) undergoes a transannular cyclisation, as shown in figure S.1 forming the tricyclic species (50), (52), and (53) and (48), which contain a cyclopropyl ring. These species have not been detected. However, species (44), (45) , (46), and (40), which form by the further reaction of the cyclopropyl based intermediates with the oxides of nitrogen, have been isolated and characterised. Three nitroxide radicals are detected when humulene nitrosite is reacted with N2O3. These radicals are postulated to form as shown in figure S.1. It has been demonstrated, that nitroxide radicals are not formed by the direct attack of NO2 at the pi system of humulene nitrosite, as shown in figure 5.1, but instead NO2 can replace the nitroso group of humulene nitrosite forming the cis and trans isomers of dinitro-humulene (24), with a subsequent addition of NO2 over the remaining double bonds, forming (38) and (39). Topic two: The photolysis reactions of humulene nitrosite when irradiated with red light Humulene nitrosite exists in two crystalline forms, which consist of needles or platelets, and both forms produce the same paramagnetic species when irradiated with red light. In all, six different nitroxide radicals have been generated photochemically from humulene nitrosite. Four nitroxide radicals (19a), (19b), (20), and (21) are obtained when crystalline humulene nitrosite, or solutions of the nitrosite in the aprotic solvents chloroform, toluene, and benzene are irradiated with red light. A fifth nitroxide radical (29) is generated by irradiating solid solutions of humulene nitrosite (17) in dinitro-humulene (24) with red light. (Abstract shortened by ProQuest.).

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Organic chemistry
Date of Award: 1977
Depositing User: Enlighten Team
Unique ID: glathesis:1977-78776
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Jan 2020 14:55
Last Modified: 30 Jan 2020 14:55
URI: http://theses.gla.ac.uk/id/eprint/78776

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