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Studies on the Disproportionation and Other Reactions of Secondary Phosphine Oxides.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Studies on the Disproportionation and Other Reactions of Secondary Phosphine Oxides./
作者:	Kydd, Douglas W. B.
面頁冊數:	1 online resource (254 pages)
附註:	Source: Dissertations Abstracts International, Volume: 80-11, Section: C.
Contained By:	Dissertations Abstracts International80-11C.
標題:	Inorganic chemistry. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=13894644click for full text (PQDT)
ISBN:	9781392133897

Studies on the Disproportionation and Other Reactions of Secondary Phosphine Oxides.
Kydd, Douglas W. B.

Studies on the Disproportionation and Other Reactions of Secondary Phosphine Oxides. - 1 online resource (254 pages)

Source: Dissertations Abstracts International, Volume: 80-11, Section: C.

Thesis (Ph.D.)--The University of Manchester (United Kingdom), 1972.

Includes bibliographical references

A large number of secondary phosphine oxides, R2P(O)H, were prepared by the reaction between the corresponding Grignard reagent and diethyl phosphonate. Isolation of the diarylphosphine oxides was more difficult than in the case of the dialkylphosphine oxides as the former were less stable and more difficult to distil on account of their ease of dispaoportionation. The reaction between tertiary-butylmagnesiura chloride and diethyl phosphonate was shown to give good yields of the ethyl tertiary-butylphosphonite which had been previously prepared by another route v the second ester group being unable to react with the Grignard reagent due to the steno hindering effect of the first tertiary-butyl gnaup. Di-tertiary-butylphosphine oxide was prepared by hydrolysis of the di-tertiary-butylphosphinous chloride as previously reported. The reaction between tertiary-butylmagnesium chloride and phosphorus tribromide was found to give a better yield of the di-tertiary-butyl-phosphinous bromide compared to the yield of the di-tertiary-butyl-phosphinous chloride from the corresponding reaction between the tertiary-butylmagnesium chloride and phosphorus trichloride. The hydrolysis of di-tertiary-butylphosphinous bromide by water/bensene yielded the di-tertiary-butylphosphine oxide-hydrobromide salt formed by reaction of the weak di-tertiary-butylphosphine oxide base with the hydrobromic acid, liberated on hydrolysis of the phosphinous bromide. Di-(2,4,6-trimethylphenyl) phosphine oxide and di-(2,3,5,6-tetramethylphenyl) phosphine oxide were prepared from the aryl bromides and diethyl phosphonate. The two phosphine oxides were oxidised to phosphinic acids and the structure of all four ccimpounds was confirmed by their n.m.r. spectra. Comparison of the products with those previously reported from the reactions of mesitylene (1,3,5-trimethylbenzene) and durene (1,2,4,5-tetramethylbenzene) with phosphorus trichloride and aluminium chloride showed that migration of methyl groups occurs during the aluminium chloride catalysed reactions. Some mono-substitution was found at the molar ratio of mesitylene to phosphorus tricbloride previously used but this was avoided by using an excess of hydrocarbon. Crude distillations of these secondary phosphine oxides at varying temperatures under reduced pressures gave no Correlation between the different attached organic groups and the ease of disproportionation of the phosphine oxides to the phosphine and phosphinic acid. Howeverx addition of traces of acid caused disproportionation of all_the phosphine oxides except those having R = But, iso-C3H7, 2,4,6-trimethylphenyl and 2,3,5"6-tetramethyl-phenyl0. Addition of 2-3 pellets of potassium hydroxide facilitatea the distillation of most of the secondary phosphine oxides with no disproportionation. Mineral acid was required to catalyse the disproportionation and it was shown that the phosphinic acids would not catalyse this decomposition. More exact disproportionation kinetic studies were carried out using di-iso-pantylphosphine oxide as its melting point (35°) facilitated sample preparation. Mineral acid was added to those samples in the form of constant boiling hydrochloric acid. These kinetics Showed that the disproportionation was second or third order in phosphine oxide had a normal activation energy but a rather low pre-exponential factor indicating a highly ordered transition state. This highly ordered transition state had been previously indicated by the lack of disproportionation of secondary phosphine oxides with congested groups. Samples of phosphine oxide with high acid concentrations were observed to contain considerable amounts of hydrogen after being heated in the disproportionation kinetic runs. Hydrogen evolution was shown to be due to oxidation of the phosphine oxide by water or chloride ion and a mechanism was proposed. Studies with varying concentrations of water (i.e0 using dilute and concentrated hydrochloric acid as a catalyst instead of constant boiling acid) showed that the rate of the disproportionation reaction was dependent on the concentration of acid but also inhibited by water. Kinetics were attempted under anhydrous conditions in 1-methyl-naphthalene and E-xylone containing dry hydrogen chloride gas. It was shown that the rate of disproportionation was greatly increased by the absence of water. Useful kinetics, especially the more accurate determination of the reaction order by dilute solution kinetics, could not be carried out due to the existence of a competing isomerisation, inferred from changes in the n.m.r. spectrum of the protonated phosphine oxide. In view of the overall evidence, mechanism, in which a phosphine oxide dimer or trimer, protonated on oxygen, is fanned in a series of equilibria and then undergoes a rate determining unimolecular deprotonation from phosphorus accompanied by a transfer of oxygen, are proposed.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9781392133897Subjects--Topical Terms:

3173556
Inorganic chemistry.
Subjects--Index Terms:

Phosphine oxidesIndex Terms--Genre/Form:

542853
Electronic books.

Studies on the Disproportionation and Other Reactions of Secondary Phosphine Oxides.
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504 $a Includes bibliographical references
520 $a A large number of secondary phosphine oxides, R2P(O)H, were prepared by the reaction between the corresponding Grignard reagent and diethyl phosphonate. Isolation of the diarylphosphine oxides was more difficult than in the case of the dialkylphosphine oxides as the former were less stable and more difficult to distil on account of their ease of dispaoportionation. The reaction between tertiary-butylmagnesiura chloride and diethyl phosphonate was shown to give good yields of the ethyl tertiary-butylphosphonite which had been previously prepared by another route v the second ester group being unable to react with the Grignard reagent due to the steno hindering effect of the first tertiary-butyl gnaup. Di-tertiary-butylphosphine oxide was prepared by hydrolysis of the di-tertiary-butylphosphinous chloride as previously reported. The reaction between tertiary-butylmagnesium chloride and phosphorus tribromide was found to give a better yield of the di-tertiary-butyl-phosphinous bromide compared to the yield of the di-tertiary-butyl-phosphinous chloride from the corresponding reaction between the tertiary-butylmagnesium chloride and phosphorus trichloride. The hydrolysis of di-tertiary-butylphosphinous bromide by water/bensene yielded the di-tertiary-butylphosphine oxide-hydrobromide salt formed by reaction of the weak di-tertiary-butylphosphine oxide base with the hydrobromic acid, liberated on hydrolysis of the phosphinous bromide. Di-(2,4,6-trimethylphenyl) phosphine oxide and di-(2,3,5,6-tetramethylphenyl) phosphine oxide were prepared from the aryl bromides and diethyl phosphonate. The two phosphine oxides were oxidised to phosphinic acids and the structure of all four ccimpounds was confirmed by their n.m.r. spectra. Comparison of the products with those previously reported from the reactions of mesitylene (1,3,5-trimethylbenzene) and durene (1,2,4,5-tetramethylbenzene) with phosphorus trichloride and aluminium chloride showed that migration of methyl groups occurs during the aluminium chloride catalysed reactions. Some mono-substitution was found at the molar ratio of mesitylene to phosphorus tricbloride previously used but this was avoided by using an excess of hydrocarbon. Crude distillations of these secondary phosphine oxides at varying temperatures under reduced pressures gave no Correlation between the different attached organic groups and the ease of disproportionation of the phosphine oxides to the phosphine and phosphinic acid. Howeverx addition of traces of acid caused disproportionation of all_the phosphine oxides except those having R = But, iso-C3H7, 2,4,6-trimethylphenyl and 2,3,5"6-tetramethyl-phenyl0. Addition of 2-3 pellets of potassium hydroxide facilitatea the distillation of most of the secondary phosphine oxides with no disproportionation. Mineral acid was required to catalyse the disproportionation and it was shown that the phosphinic acids would not catalyse this decomposition. More exact disproportionation kinetic studies were carried out using di-iso-pantylphosphine oxide as its melting point (35°) facilitated sample preparation. Mineral acid was added to those samples in the form of constant boiling hydrochloric acid. These kinetics Showed that the disproportionation was second or third order in phosphine oxide had a normal activation energy but a rather low pre-exponential factor indicating a highly ordered transition state. This highly ordered transition state had been previously indicated by the lack of disproportionation of secondary phosphine oxides with congested groups. Samples of phosphine oxide with high acid concentrations were observed to contain considerable amounts of hydrogen after being heated in the disproportionation kinetic runs. Hydrogen evolution was shown to be due to oxidation of the phosphine oxide by water or chloride ion and a mechanism was proposed. Studies with varying concentrations of water (i.e0 using dilute and concentrated hydrochloric acid as a catalyst instead of constant boiling acid) showed that the rate of the disproportionation reaction was dependent on the concentration of acid but also inhibited by water. Kinetics were attempted under anhydrous conditions in 1-methyl-naphthalene and E-xylone containing dry hydrogen chloride gas. It was shown that the rate of disproportionation was greatly increased by the absence of water. Useful kinetics, especially the more accurate determination of the reaction order by dilute solution kinetics, could not be carried out due to the existence of a competing isomerisation, inferred from changes in the n.m.r. spectrum of the protonated phosphine oxide. In view of the overall evidence, mechanism, in which a phosphine oxide dimer or trimer, protonated on oxygen, is fanned in a series of equilibria and then undergoes a rate determining unimolecular deprotonation from phosphorus accompanied by a transfer of oxygen, are proposed.
533 $a Electronic reproduction. $b Ann Arbor, Mich. : $c ProQuest, $d 2023
538 $a Mode of access: World Wide Web
650 4 $a Inorganic chemistry. $3 3173556
650 4 $a Organic chemistry. $3 523952
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773 0 $t Dissertations Abstracts International $g 80-11C.
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=13894644 $z click for full text (PQDT)