885. Nitration at nitrogen and oxygen centres. Part II. Kinetics and mechanism of the conversion of alcohols, glycols, and glycerol into their nitric esters

Abstract

The O-nitrations of methyl alcohol, pnitrobenzyl alcohol, ethylene glycol, trimethylene glycol, and also glycerol with respect to its primary hydroxyl groups, with nitric acid in constant excess in solvent nitromethane of nottoo-high water-content, are of zeroth-order and identical in absolute rate with one another and with the N-nitrations of N-methyl-di-or -tri-nitroaniline and with the C-nitrations of benzenoid hydrocarbons under the same conditions. For the nitration of methyl alcohol small concentrations of sulphuric acid increase, of nitrate ions decrease, and of water do not change the zeroth-order rate, whilst larger concentrations of water increase it, and still larger concentrations cause a switch from zeroth-t o first-order kinetics with reduction in the absolute rate. I n the presence of sufficient water to secure first-order kinetics, the rates of attack of nitronium ion on the unsaturated or unshared electrons of carbon, nitrogen, and oxygen in the substances mentioned were compared.In conditions similar to those of these zeroth-order nitrations, neopentyl alcohol is nitrated in a kinetic form between zeroth and first order, and a t a smaller absolute rate, whilst the secondary hydroxyl group, remaining after the nitration of glycerol has completed its zeroth-order course, is nitrated in first-order form, and a t a still smaller rate.AS NOTED in the preceding paper, we expect that, for any one general reaction within the natural family of electrophilic substitutions, for instance, nitration, nitrosation, or chlorination, much the same pattern of available mechanisms will apply to C-, N-, and O-substitutions. In particular, we expect that, since in C-nitration the nitronium-ion mechanism is outstandingly important, this mechanism will probably dominate the picture of Nand O-nitrations.We are here concerned with O-nitrations, particularly with the conversions of alcohols into alkyl nitrates. Until recently, such esterifications with nitric acid seem not to have been generally regarded, at least not automatically, as nitrations. In 1950 Israelashvili suggested that the conversion of starch into its nitrate might be an O-nitrati0n.l In 1951, KIein and Mentser proved, by the use of isotopically labelled oxygen, that the conversion of cellulose into its nitrate was indeed an O-nitration: what was shown was that, for each group C-0-H converted, the replacement was of H by NO,, with two oxygen atoms from the nitrating medium, not of OH by NO,, with three oxygen atoms from that source.2 This work firmly classified the esterifications of alcohols with nitric acid as nitrations, but left untouched the question of nitration mechanism.The nitronium-ion mechanism of the O-nitration of alcohols was first identified in this research by the kinetic method originally developed (refs. 1 and 2 of preceding paper) for the study of aromatic C-nitration, the principle of which is to show that a conjugate acid of nitric acid is dehydrated to a nitrating entity, which, according to how we adjust the competitive conditions, ...

Separation of Diastereomeric and Enantiomeric Alkyl Nitrates–Systematic Approach to Chiral Discrimination on Cyclodextrin LIPODEX‐D

“…The alcohols were obtained from Aldrich (Steinheim, Germany), Fluka (Buchs, Switzerland), Janssen Chimica (Geel, Belgium), Merck (Darmstadt, Germany), Merck-Schuchardt (Hohenbrunn, Germany) and Riedi de Haen (Seelze, Germany). The reaction mechanism is known to be an electrophilic substitution of the proton for the nitryl cation NO: [32,33]. The advantage of this reaction is that the oxygen atom remains attached to the alcohol, and the configuration of the asymmetric carbon atom is thus preserved.…”

2,2-Bis(trifluoromethyl)-1,2-dihydropyrimidinium salts

“…Caled for CiiHaFi2N20: C, 32.1; , 1.7; N, 6.8. Found: C, 31.9; , 1.9; N, 6.8. 2,2-Bis(trifluoromethyl)-l,2-dihydropyrimidinium Chloride (6). Hydrogen chloride was passed through a solution of 5 g of 2 and 3.7 g of 1,3,3-trimethoxy-l-propene in 500 ml of dry benzene for 5 min.…”

Kinetic Modelling of Nitration of Glycerol: Three Controlling Reactions Model

“…The primary hydroxyl group is more reactive than secondary hydroxyl group. Previous studies [22][23] showed that hydroxyl group at secondary position less reactive than primary position because of steric hindrance. Steric hindrance causes the transition state to be higher in energy and raise activation energy of reaction.…”