Mark C. Whiting

A versatile process for the syntheses of very long chain alkanes, functionalised derivatives and some branched chain hydrocarbons

An earlier method for synthesising very long straight-chain alkanes of very specific lengths has been improved to give, in some cases, gram amounts of materials. Eleven compounds have been made: C98H198, C122H246, C162H326, C194H390, C198H398, C210H422, C242H486, C246H494, C258H518, C294H590 and C390H782. The self-condensation reaction of one of the intermediate aldehydes enabled two chain-branched hydrocarbons to be obtained: C96H193CHRC94H189 where R = CH3 and CH3(CH2)3. Three long-chain compounds containing carboxylic acid groups have been prepared: CH3(CH2)190CO2H,HO2C(CH2)48CO2H and HO2C(CH2)192CO2H.

Studies on the synthesis of linear aliphatic compounds. Part. 3 The synthesis of paraffins with very long chains

The approach derived in Part 2 has been modified to increase the purity and yield of intermediates. The C12 starting materials have been doubled in chain length five times, and by using components of similar or different chain length in Wittig condensations ω-halogeno-acetals with 12n carbon atoms have been made up with n up to 32. They have been converted into paraffins with 102, 104, 150, 198, 246, 294, and 390 carbon atoms. Those paraffins with 150 or more carbon atoms show chain-folding in the crystalline state; this observation is contributing to the understanding of chain-folding behaviour long known in linear polyethylene but hitherto unknown in essentially pure paraffins.

The synthesis of pure n-paraffins with chain-lengths between one and four hundred

Syntheses are described for pure paraffins having 102, 150,198, 246, and 390 carbon atoms; unlike lower homologues, all but the first show interesting properties in the solid state, bridging the gap between the chain-extended and the chain-folded modes of crystallisation typical of the lower n-paraffins and the linear polyethylenes, respectively.

Kinetics and mechanism of N–H and C–H isotopic exchange in pyrrole and indole: acid-catalysed exchange in aqueous acetonitrile solutions

The deuteriodeprotonation of the N–H and of the α- and β-C–H positions in pyrrole, and of the N–H and β-C–H positions in indole, has been studied kinetically as a function of the concentration of perchloric acid, medium composition, and temperature in aqueous (2H2O) acetonitrile solutions. The N–H exchange process was followed using the first overtone of the N–H stretching mode. Ancillary i.r. studies define the molecular states of the reactants. The Hammett H0 acidity function is reported for dilute perchloric acid in acetonitrile-water mixtures. Bunnett w values clarify differences between the hydration of the N–H and C–H exchange transition states.

The synthesis of long-chain unbranched aliphatic compounds by molecular doubling

A convenient General synthesis, applicable to alkanes and terminally mono- and di-substituted alkanes of any chain length, is described; cyclododecanone is used as the starting material, and the C12 chain is doubled in length as often as required and adjusted first to a multiple of 12, and than to any desired length.

Classical carbonium ions. Part 11. Solvent effects on solvolysis rates: the Grunwald–Winstein equation

Although originally proposed for ‘limiting’ solvolyses in any solvent, the Grunwald–Winstein equation accurately fits the reactions of 1-methylethyl toluene-p-sulphonate in water–ethanol mixtures, which are known to be non-limiting. Solvolyses of 1-adamantyl derivatives (picrate and toluene-p-sulphonate) cannot involve nucleophilic assistance, yet in solvent systems like methanol–tetramethylene sulphone or ethanol–chloroform, seriously non-linear Grunwald–Winstein plots are observed. In an alternative treatment of the data, the solvolysis of 1-adamantyl picrate in methanol–tetramethylene sulphone is shown, by the remarkable insensitivity to solvent composition of its rate and its entropy of activation, to be a particularly simple process mechanistically. The relationship between the activity of the alcohol component and the solvolysis rate indicates that in the other three systems studied, the alcohol molecules participate stoicheiometrically in hydrogen bonding to the incipient anion. Criteria for linear Grunwald–Winstein plots can therefore be suggested.

Convenient syntheses of bifunctional C12-acyclic compounds from cyclododecanone

The conversion of cyclododecanone by convenient, non-hazardous, and high-yielding reactions into a set of useful C12-bifunctional intermediates is described. Baeyer–Villiger oxidation and hydrolysis give a hydroxy acid, successively converted into the bromo acid, bromo alcohol, crude bromo aldehyde, pure bromo aldehyde ethylene acetal, and pure bromo aldehyde. Preferred reagents for the transformation CO2H → CHO are borane–dimethyl sulphide followed by dimethyl sulphoxide–oxalyl dichloride–triethylamine.

Studies on the synthesis of linear aliphatic compounds. Part 2. The realisation of a strategy for repeated molecular doubling.

Routes from C11 and C12 starting-materials, obtainable free from near homologues, to compounds of doubled chain length have been explored as approaches to the synthesis of n-paraffins and of terminally mono- or bi-functional derivatives. Acetylene alkylation routes lead to problems with protecting groups, but the use of the Wittig reaction provides a method of molecular doubling convenient for repeated use, with the formation of chain-lengths rising in a geometrical progression. The general problems inherent in the synthesis of very long-chain paraffins are discussed, earlier work is reviewed, and criteria for success are suggested. A useful protecting group for hydroxyl, the tri-p-tolylmethyl (trimtyl) ether, is described.

Kinetics and mechanism of N–H and C–H exchange in pyrrole and indole. Part II. General acid catalysed exchange in aqueous acetonitrile

Rates of hydrogen exchange at N, Cα, and Cβ in pyrrole, and at N, and Cβ in indole, are reported for various 2H2O-acetonitrile solutions containing trichloroacetic acid as catalyst. I.r. studies established the molecular state and the approximate pKa of trichloroacetic acid in this system. The observation of general acid catalysis suggests a common A-SE2 exchange mechanism for both N–H and C–H exchange reactions. As the solvent composition is changed, the apparent Ho acidity function, and the rates of Cα–H and Cβ–H exchange, do not follow parallel curves because of differences between the hydration of the conjugate acid of the indicator and the transition state for exchange. The relative rate of exchange at Cα and Cβ in pyrrole in this system differs significantly from that in the 2H2O-acetonitrile-HClO4 system.

Classical carbonium ions. Part 10. Selectivity in the solvolytic products from 1-adamantyl derivatives in aqueous ethanol

The relative proportions of adamantan-1-ol and its ethyl ether obtained when 1-adamantyl bromide, picrate, 2,4-dinitrophenolate, and toluene-p-sulphonate undergo solvolysis at 100 °C in aqueous ethanol were measured at four solvent compositions. Differences between the four substrates were observed, implying ion-pair involvement, and variations with solvent composition which are attributed to differences in the ability of the various ion-pairs to select a molecule of water or of ethanol in forming a solvent-separated ion-pair.