Kinetic studies in the solvents acetic acid and acetic anhydride. Part I.—Properties of the solvo-system

MacKenzie, H. A.; Winter, E. R. S.

doi:10.1039/tf9484400159

Cited by 38 publications

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“…T h e rate constant increases faster than a measured acidity function (HO) (1G) in the solvent mixture, and the rate constant for dithioacetal substitution, u~llike anomerization, reaches a maximum near 90% acetic anhydride. At this solvent composition, acetic acid (in acetic anhydride) is almost co1npletelj7 dissociated t o inonoiller (16). Apparently the ratio o f f substrate conjugate acid to f* becomes larger (at higher acetic anhydride concentration) when the substrate is the dithioacetal than when the substrate is glucose pentaacetate.…”

Section: Resultsmentioning

confidence: 88%

SUBSTITUTION OF ACYCLIC SUGAR ACETALS: RATE OF PERCHLORIC ACID CATALYZED ACETOLYSIS OF 2,3,4,5,6-PENTA-O-ACETYL-D-GLUCOSE DIETHYL DITHIOACETAL AND 1,2,3,4,5,6-HEXA-O-ACETYL-D-GLUCOSE S-ETHYL MONOTHIOACETAL

Kurihara¹,

Painter²

1966

Can. J. Chem.

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The rate constants for the perchloric acid catalyzed substit~~tion ol one ethylthio group 01 ~,~,4,5,6-penta-O-acetyl-~-ficose diethyl dithioacetal (Va) and the acetoxy group bonded to CI of 1,2,3,4,5,6-hexa-0-ncetyl-D-glucose S-ethyl monothioacetal (VIa) have been ~neasured when the substrates were dissolved in solutions of acetic acid and acetic anhydride. ?'he ratedetermining step is interpreted to be the dissociation of the substrate c o n j~~g a t e acid to give a carbonium-sulfonium cation. The rate constants indicate that acyclic sugar derivatives are substituted faster than cyclic (pyranose) derivatives, and that a n acetosy group is substituted faster than an ethylthio group.Acetals dissolved in mixtures oi acetic acid and acetic anhydride \\-hich contaiil a strong acid give substitution products \vhich arise by cleaving either C-0 bond of the substrate. The product has a C-OAc bond in place of the C-0 bond cleaved. Thus mcthyl 2,3,4-tri-0-acetyl-P-arabinoside (I) gave both I1 and I11 \vhen the acid \\-as zinc chloride or 0.16y0 sulfuric; and gave the C l gem-diacetate (I\'), a product \\-hich required cleavage of both the C1-OCI13 and C1-0 ring bonds of I, when the catalyst \\-as 4y0 ssulfuric acid (1).Poly-0-acetyl diethyl dithioacetals of the comnzon monosaccl~arides behave in much the same n7ay. Pirie (2) dissolved dithioacetals (V) in acetic anhydride which contained 1.8 Msulfuric acid, and isolated products (Cl gem-diacetates (1'11)) for~ned by s u b s t i t~~t i o n after cleavage of each ethylthio group. Sinlilar to the observation of A,Iontgomery ef nl. (1) \\-hen I \\-as the substrate, acids a t lo~v concentration catalyze a fast substitution of one For personal use only.

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Section: Resultsmentioning

confidence: 88%

SUBSTITUTION OF ACYCLIC SUGAR ACETALS: RATE OF PERCHLORIC ACID CATALYZED ACETOLYSIS OF 2,3,4,5,6-PENTA-O-ACETYL-D-GLUCOSE DIETHYL DITHIOACETAL AND 1,2,3,4,5,6-HEXA-O-ACETYL-D-GLUCOSE S-ETHYL MONOTHIOACETAL

Kurihara¹,

Painter²

1966

Can. J. Chem.

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“…The kinetics and mechanism of acetoxylation have been described (82). Although the acetylium ion is an electrophile, extensive studies of electronic effects show a definite relationship to nucleophilic-addition chemistry (83).…”

Section: ð36þmentioning

confidence: 99%

Quinones

Finley

2016

Kirk-Othmer Encyclopedia of Chemical Technology

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Quinones, possessing two α,β‐unsaturated carbonyl groups usually in a six‐carbon atom ring, represent a unique structural unit. Their centrality in the synthesis of such important commercial substances as dyes and pharmaceuticals has resulted in extensive studies. In living matter, they are ubiquitous and vital to human metabolism. Quinones are of special interest to biochemists and to both synthetic and theoretical organic chemists. The types of reactions most often reported are nucleophilic addition, photochemistry, cycloaddition, electrophilic addition, radical alkylation, electrochemical, oxidation, and nucleophilic substitution. The synthesis of quinones is usually accomplished through oxidation of phenols or anilines.

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“…[211 On the other hand the constant in equation [12] is proportional to (HN03)4, while (N020Hz+) is proportional to k , , so that elimination of (Nos-) between [12] [241 Finally, since p = (NO3-), it follows from [21] and the expression for the equilibri~im constant of [20] …”

Section: Order Of Reaction With Respect To Nitric Acidmentioning

confidence: 99%

“…This equation neglects the extent of dimerization of acetic acid (12) and the possible greater basicity of acetic acid as compared with acetic anhydride, both of which become increasingly important effects a t higher concentration of acetic acid. The latter effect would increase the nitrate ion concentration and thereby tend to repress the formation of nitracidium ion.…”

Section: Exptmentioning

confidence: 99%

“…Also, from equation [12] and the proportionality between k, and (N020H2+), k,,Lyf2 = const. CIGI Differentiating [14'] and [16] with respect to x, eliminating dy/dx between these equations, taking the limit of the resultant equation a t x = 0 and neglecting a very small term involving df/dx (which is justified at x = 0) Using this equation, the concentration of nitrate ion, y, a t x = 0 was estimated from the limiting slope of a plot k,, vs. x (cf.…”

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confidence: 99%

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STUDIES OF RDX AND RELATED COMPOUNDS: XI. THE CONVERSION OF PHX TO AcAn

Marcus¹,

Winkler²

1953

Can. J. Chem.

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The formatioli of AcAli from PI-IX, nitric acid, and acetic anhydride has been investigated a t various teniperatures. The effects of added acetic acid and added salts have bee11 determined. While the reaction is first order with respect to PHX, it is of a n order 2.6 with respect to nitric acid. The reaction rate is significantly decreased by snlall co~icentrations of sodium nitrate. The reactjon is also characterized by a secondary salt effect and a low apparent actlvatlou energy of about 2 Itcal. mole-'. A mechanism has been suggested ill qualitative, and to sonle extent quantitative, agreement with the experimental data. I t is postulated that the conversion of P H X involves a rate-controlling ionic reaction between P H X and nitric acid, and that this is followed by a rapid acetylation of the acidic intermediate to AcAn.

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Kinetic studies in the solvents acetic acid and acetic anhydride. Part I.—Properties of the solvo-system

Cited by 38 publications

References 0 publications

SUBSTITUTION OF ACYCLIC SUGAR ACETALS: RATE OF PERCHLORIC ACID CATALYZED ACETOLYSIS OF 2,3,4,5,6-PENTA-O-ACETYL-D-GLUCOSE DIETHYL DITHIOACETAL AND 1,2,3,4,5,6-HEXA-O-ACETYL-D-GLUCOSE S-ETHYL MONOTHIOACETAL

SUBSTITUTION OF ACYCLIC SUGAR ACETALS: RATE OF PERCHLORIC ACID CATALYZED ACETOLYSIS OF 2,3,4,5,6-PENTA-O-ACETYL-D-GLUCOSE DIETHYL DITHIOACETAL AND 1,2,3,4,5,6-HEXA-O-ACETYL-D-GLUCOSE S-ETHYL MONOTHIOACETAL

Quinones

STUDIES OF RDX AND RELATED COMPOUNDS: XI. THE CONVERSION OF PHX TO AcAn

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