Studies on Reactions Relating to Carbohydrates and Polysaccharides. XLVII. The Oxygen Valence Angle and the Structure of Glucose and Related Compounds<sup>2</sup>

Allen, J. S.; Hibbert, Harold

doi:10.1021/ja01321a058

Cited by 34 publications

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“…The dipole moment of propylene oxide found in this study is in good agreement (Table 5) with previously reported values (16,17,21). The decreasing preponderance of polar conformers with increasing size of halogen is obvious from the trend in the series.…”

Section: Experitnental Dipole Monzentssupporting

confidence: 92%

Nuclear magnetic resonance spectra of the epihalohydrins: II. Spectral analyses and structural correlations for all the epihalohydrins

Macdonald¹,

Reynolds²

1970

Can. J. Chem.

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Complete analyses of the proton magnetic resonance spectra of propylene oxide, epifluorohydrin, epibromohydrin, and epiiodohydrin shows that in all cases the cisoidcoupling constants over four bonds are negative, and the trarzsoid coupling constants positive. Dipole moments, together with the vicinal coupling constants of the CH-CH2X moiety, are used to establish the probable confornlations for all the epihalohydrins. Conformational factors appear to obscure any possible relationship between substituent electronegativity and long-range coupling constants. Canadian Journal of Chemistry, 48, 1046 (1970) IntroductionAlthough the epihalohydrins, 1 (X = F, C1, Br, I), have been investigated previously by nuclear magnetic resonance (n.m.r.) spectroscopy (1-5), the published data are incomplete, especially with regard to the signs and magnitudes of the long-range proton-proton coupling constants (4JHH). A recent unequivocal sign determination for epichlorohydrin by one of us (6) has buttressed the conclusion that care is required in the spectral analysis of this series of compounds (7).

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Section: Experitnental Dipole Monzentssupporting

confidence: 92%

Nuclear magnetic resonance spectra of the epihalohydrins: II. Spectral analyses and structural correlations for all the epihalohydrins

Macdonald¹,

Reynolds²

1970

Can. J. Chem.

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“…Protonation of the carbenes 17b, 31, and 53 is clearly indicated by their product ratios and, for 31, by the formation of isomeric ethers (33,36). The more electrophilic carbenes discriminate but slightly between oxetane and methanol while the more nucleophilic carbenes (17b, 31,53) prefer the protic methanol strongly over the aprotic oxetane.…”

mentioning

confidence: 99%

Carben‐Reaktionen mit Oxetan und mit Oxetan/Methanol‐Gemischen

1991

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Reactions of Carbenes with Oxetane and with OxetaneJMethanol MixturesEthoxycarbonylcarbene, bis(methoxycarbonyl)carbene, phenylcarbene (17a), diphenylcarbene (l?b), fluorenylidene ( I~c ) , 2-furylcarbene (31 a], 2-furyl(phenyl)carbene (31 b), 4-oxo-2,5-cyclohexadienylidene (40), and 4,4-dimethyl-2,5-cyclohexadienylidene (53) were generated by photolysis of the appropriate diazo compounds. With neat oxetane, most of these carbenes react by competitive C -H insertion (B -+ A, Scheme 1) and ylide formation (B -+ C). 31a and 40 do not insert into C -H bonds; 31 b does not attack oxetane but rearranges exclusively with formation of 26. The ylides undergo Stevens rearrangement to give tetrahydrofurans (C -+ D) and a'$-elimination, leading to ally1 ethers (C + E). With oxetane/rnethanol mixtures, the intervention of oxonium ions (H) is indicated by the formation of 1,3-dialkoxypropanes (I). The oxonium ions arise either by protonation of the ylides (C -+ H) or by protonation of the carbenes (B -+ G ) , followed by electrophilic attack of the carbocations (G) at oxetane (G -+ H).The former route is followed by the alkoxycarbonylcarbenes and by 40; the ylides derived from the remaining carbenes do not react with methanol, owing to their rapid Stevens rearrangements. Protonation of the carbenes 17b, 31, and 53 is clearly indicated by their product ratios and, for 31, by the formation of isomeric ethers (33, 36). The more electrophilic carbenes discriminate but slightly between oxetane and methanol while the more nucleophilic carbenes (17b, 31,53) prefer the protic methanol strongly over the aprotic oxetane.Carbene reagieren mit den nichtbindenden Elektronenpaaren von Heteroaromatcn zu Yliden'). Wahrend die Bildung von Stickstoff-, Phosphor-und Schwefel-Yliden gut untersucht ist und auch stabile Vertreter dieser Verbindungsklassen dargestellt werden konnten, weiB man uber Sauerstoff-Ylide relativ wenig. Aus Alkylethern entstehen Ylide, die nicht umlagern, sondern durch Spuren von Wasser oder Alkoholen protoniert und dann nucleophil gespalten werden'). Formale C -0-Einschiebung erfolgt bei Benzylethern und Allylethern4); fur letztere weist Allyl-Inversion auf eine 2,3-sigmatrope Ylid-Umlagerung hin. Arylcarbene mit geeigneten Seitenketten zeigen intramolekulare Einschiebung in 0-Benzyl-und O-Allyl-Bind~ngen~). Tetrahydrofuran reagiert mit Methylen nur in der Gasphase, nicht aber in Losung unter Ringerweiterung6'. Dagegen beobachteten wir bei der Belichtung von Diazomethan in Oxetan (1) ca. 40% C -0-Einschiebung'). Weitgehende Racemisierung bei der Ringerweiterung von (S)-ZMethyloxetan (2) zu 3-Methyltetrahydrofuran (3) sprach fur einen radikalischen Mechanismus dcr Stevens-Umlagerung8).In dieser Arbeit berichten wir iiber die Reaktionen weiterer Carbene mit Oxetan und Oxetan/Methanol-Gemischen. Der Zusatz von Methanol dient zum Abfangen in-3 ( 2 7 % )termediarer Ylide, gibt aber auch Einblick in das Verhalten der Carbene gegenuber 0 -H-Bindungen. Alkox ycarbon ylcarbeneBei

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“…The calculation of the moment of 1,3-dioxane referred to above (I) made use of an assumed moment for the C-0-C group of 1.25 D l which is one experimental value of the dipole moment of dimethyl ether. However, in general the C-0-C group appears to have a higher moment in cyclic ethers, the dipole moment of pentamethylene oxide, for example, being 1.87 D (8). In addition, the presence of two C-0-C groups in the ring will change the charge distribution in such a way as to reduce the effective dipole moment associated with each.…”

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confidence: 99%

The Dielectric Constant and Dipole Moment of 1,3-Dioxane

Walker¹,

Davidson²

1959

Can. J. Chem.

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Studies on Reactions Relating to Carbohydrates and Polysaccharides. XLVII. The Oxygen Valence Angle and the Structure of Glucose and Related Compounds²

Cited by 34 publications

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Nuclear magnetic resonance spectra of the epihalohydrins: II. Spectral analyses and structural correlations for all the epihalohydrins

Nuclear magnetic resonance spectra of the epihalohydrins: II. Spectral analyses and structural correlations for all the epihalohydrins

Carben‐Reaktionen mit Oxetan und mit Oxetan/Methanol‐Gemischen

The Dielectric Constant and Dipole Moment of 1,3-Dioxane

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Studies on Reactions Relating to Carbohydrates and Polysaccharides. XLVII. The Oxygen Valence Angle and the Structure of Glucose and Related Compounds2

Cited by 34 publications

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Nuclear magnetic resonance spectra of the epihalohydrins: II. Spectral analyses and structural correlations for all the epihalohydrins

Nuclear magnetic resonance spectra of the epihalohydrins: II. Spectral analyses and structural correlations for all the epihalohydrins

Carben‐Reaktionen mit Oxetan und mit Oxetan/Methanol‐Gemischen

The Dielectric Constant and Dipole Moment of 1,3-Dioxane

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Studies on Reactions Relating to Carbohydrates and Polysaccharides. XLVII. The Oxygen Valence Angle and the Structure of Glucose and Related Compounds²