Structure and Properties of Cyclic Compounds: Xi. Dissociation Constants of the Cyanohydrins of Some Methylcyclohexanones

Wheeler, Owen H.; Zabicky, Jacob

doi:10.1139/v58-091

Cited by 7 publications

(2 citation statements)

References 11 publications

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“…A siinilar graph for the data a t -40' gives n = 1.04 and Ii, = 13.1 moles 1.~'. These values should be compared to the very high reactivity of cyclohexanone in equilibrium reactions involving a d d i t i o~~ to the leetoile group, such as cyano11yd1-in for~natioll xvith I<, = 0.00050 in 95% ethanol (12) and IiD = 0.060 mole 1.-I i l l 80% dioxane (13) (both a t 25' C). Thc sinall difference (if real) between the dissociation constants of complex formation a t O0 and -40' C corresponds to a heat of formation ( A H ) of only +0.27 ltcal mole.…”

Section: Discussionmentioning

confidence: 99%

Interaction Between Ketone and Tertiary Amine Groups

Wheeler¹,

Levy²

1959

Can. J. Chem.

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I7apor pressure studies of trimethylamine and ketones in heptane solution have shown that unstable complexes are formed with cyclohesano~~e a t 0' and with cyclohexanone artd cyclope~~tanone a t -40'. No complex formation was observed with methylethyl ketone, diethyl ketone, or cyclopentar~one a t 0'.Robinson and co-workers (1, 2) originally suggested that there was some type of interaction between a lceto group and a tertiary arnine group in certain allcaloids having these groups in a large-membered ring, to explain the inasked reactivity of the lceto group (1) and the large displaceme~lt of its infrared stretching f r e q~~e n c y from its normal value (2). Later Leonard and co-workers (3, 4, 5) prepared a series of cyclic aza-acyloins and found evidence for transail~lular interaction in 8-(3, 5), 9-(4), and 10-(5) membered rings between the ketone and tertiary amine group. This was demonstrated by infrared and ultraviolet absorption (6) studies.Anet, Bailey, and Robinson (2) found no evidence for interaction between acetone and triethylamine or between cyclopentanone and N-methyl piperidine by infrared measurements in chloroform solution. However, the amine would preferentially interact with the chloroform (7) and hinder association between the amine and ketone, and the evidence of these worlcers cannot be considered conclusive. Thus, though interaction between lceto and amine groups within the same ring has been ainply proved, no sound evidence has been published concerning possible interaction between ketone and amine groups in separate molecules.Infrared and ultraviolet measurements are probably not the best method of observing weak interactions resulting in unstable coinplex formation, since such n~easurements must be carried out in dilute solution and cannot readily be made a t low temperatures. Moreover these measurements will only detect interactions which result in a change in the electron density of the keto group. Vapor pressure studies, however, are usually made with solutions of moderate concentration, and the lower limit of temperature is only governed by the measurable vapor pressure of one (or more) con~ponent, and the nlethod is not liinited to specific types of interaction. In this study the vapor pressure of trimethylamine above a n-heptane solution and above solutions of the lcetones, inethylethyl lcetone, diethyl ketone, cyclohexanone, and cyclopentanone in n-heptane has been measured. Trirnethylamine was chosen as a conveniently volatile, non-sterically hindered anline and ~nethylethyl lcetone and diethyl lcetone as examples of reactive and unreactive acyclic lcetones, and cyclohexanone and cyclopentanone as examples of a very reactive and a moderately reactive cyclic lcetone. The results are expressed in terms of Henry's law (8) (P solute = I<. N solute) and negative deviatioils are assumed to be due t o complex formation (8) caused by interaction between the ketones and the arnine.

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Section: Discussionmentioning

confidence: 99%

Interaction Between Ketone and Tertiary Amine Groups

Wheeler¹,

Levy²

1959

Can. J. Chem.

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“…An analogous situation exists in the association reaction between substituted cyclohexanones and cyanide ion [29] , in which the attack on the carbonyl by the strong nucleophile (CN-) has been established to be rate-determining [30] . The linear relationship found between the rates of hydrolysis of (lIb -g) from analogously substituted cyclohexanones, as illustrated by the plots in Fig.…”

Section: Calculations Of Kinetic and Thermodynamic Parametersmentioning

confidence: 99%

Organic Carbonates. Part XIII. Separation of Polar and Steric Effects in the Hydrolyses of Substituted Ethylene and Trimethylene Carbonates

Katzhendler

Poles

Sard

1972

Israel Journal of Chemistry

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The rate constants, the free energies (ill;#l. the energies (LliJ#) and entropies (t.s#) of activation, and the steric parameter of substituent (Es), for both the acid and the alkaline hydrolyses of four highly branched ethylene carbonates (la -d), and 11 trimethylene carbonates (lia -k) were analysed according to Taft's procedure for a quantitative separation of polar and steric effects of alkyl substituents in the total effect of structure upon reactivity in hydrolysis. Application of Eq. (II) with a* to the most hindered substrates ("a-axial methyl effect") (lId -0 and to the moderately hindered substrates (lla -c) gave well-separated parallel straight lines for the two groups. Deviations from Eq. (II) were manifested by the rate-enhanced group of compounds, gerninally 2,2-disubstituted trimethylene carbonates (llg -k) ("2,2-Kem-dialkyl effect"), shown to exert a polar "field effect"; the assessment of its substituent constant aF· (= +0.17) is provided by Eq. (III). Analysis of 0 18 exchange experiments and MFA #vsMFB# correlation (Eq. (IV)) show that the acid-and base-catalysed reactions occur in parallel via similar transition states, the attainment of each designating the rate-determining step in both systems. A value of 0.5 kcal/mole was found for the net steric interaction (EgB -EgA) exerted by an a-axial methyl substituent on the attacking hydroxide ion in attaining the transition state. It was concluded that in alkaline hydrolysis, the transition states of compounds exhibiting an "a-axial methyl effect" should closely resemble the tetrahedral intermediate (IX), while the transition states of the 2,2-gem-dialkyl series should more closely resemble the ground-state.

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Introduction of the cyano group into the molecule

Friedrich

Wallenfels

1970

PATAI'S Chemistry of Functional Groups

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Structure and Properties of Cyclic Compounds: Xi. Dissociation Constants of the Cyanohydrins of Some Methylcyclohexanones

Cited by 7 publications

References 11 publications

Interaction Between Ketone and Tertiary Amine Groups

Interaction Between Ketone and Tertiary Amine Groups

Organic Carbonates. Part XIII. Separation of Polar and Steric Effects in the Hydrolyses of Substituted Ethylene and Trimethylene Carbonates

Introduction of the cyano group into the molecule

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