2-Octyl nitrate

Octyl nitrate cetane improvers are not compatible with a number of different elastomers used in additive storage and injection systems. The information in TABLE 6-6 demonstrates that Teflon has the best compatibility with octyl nitrate cetane improver. 

Cristol and his co-workers have carried out the hydrolysis of the optically active 2-octyl nitrate in alkaline and neutral media. The alkaline hydrolysis was performed in the presence of sodium hydroxide both in 92.6% ethanol, where the participation of the ethoxide ion should be taken into account, and in a 64% aqueous solution of dioxane. The neutral hydrolysis was carried out in a 70% acetone solution in the presence of calcium carbonate. 

By esterifying (+)2-octanol using a mixture of nitric and sulphuric acid, it was established that the nitrate produced did not undergo inversion. The (+)2-octyl nitrate obtained was heated during a period of 50 hr in a 10% alcoholic solution of sodium hydroxide. The optical rotation of all the reaction products was nil. Analysis by means of Grignard s reagent indicated 45.6% of 2-octanol, 39.8% of ketone and 14.6% of ether (by difference). A sample of the alcohol contained 76% of (+)2-octanol and 24% of racemate, i.e. 88% of (+)2-octanol and 12% of (—)2-octa-nol. 

The experiment of hydrolysing 2-octyl nitrate in a dioxane solution has been carried out with a laevo-rotatory ester. In the reaction products 2-octanol forms as the main product with some 2-octanone and a little unchanged 2-octyl nitrate. The rotation of the reaction product amounted to —3.77°, and the alcohol consisted of a mixture containing 42% of (-)2-octanol and 58% of racemate, i.e. 71% (-)2-octanol and 29% (+)2-octanol. 

By hydrolysis of a dextro-rotatory 2-octyl nitrate in a neutral medium, this compound has been decomposed to yield a laevo-rotatory product containing 13% of 2-octanone and 87% of 2-octanol, the latter comprising 71% of (-)2-octanol and 29% racemate, i.e. 85.5 parts of laevo-rotatory and 14.5 parts of dextro-rotatory alcohol. 

It can be concluded from these experimental results that in alkaline media the 2-octyl nitrate behaves like a typical ester (Day and Ingold (50]). In neutral media, on the other hand, it behaves like an alkyl halogenide or like an ester of sulphuric acid. 

Cristol also established in the work cited that the hydrolysis of 2-octyl nitrate cannot be performed with dilute sulphuric acid. In the presence of 10% sulphuric acid as much as 99 parts of alcohol having the same rotation as the original nitrate were formed. With 70-90% sulphuric acid, 2-octanone and nitrogen oxides were formed. 

According to Merrow and van Dolah [51] (+)2-octyl nitrate reacts with hydrazine at room temperature to yield 84% (+)2-octanol, whilst by the reaction of the laevo-rotatory nitrate and ammonium polysulphide as much as 99 parts of (-)2-octanol are produced. The fact that to a large extent the original rotation was preserved indicates that in the cases cited the initial step was rupture of the N—O bond. 

Ethylhexyl nitrate (EHN) is the most widely used cetane number improver. It is also sometimes called, octyl nitrate . EHN is thermally unstable and decomposes rapidly at the high temperatures in the combustion chamber. The products of decomposition help initiate fuel combustion and, thus, shorten the ignition delay period as compared with that of the fuel without the additive. 

Deamination of primary and secondary amines. Reaction of cyclohexylamine, nitrogen tetroxide, and DBU (or DBN) in ether at -78° furnishes cyclohexyl nitrate in 757 yield. In the absence of the base, a mixture of the nitrate, cyclo-hexanol, and another product is obtained in about 507 yield. The new conditions are also applicable to primary alkyl amines n-octylamine / -octyl nitrate (817o yield). The reaction proceeds with retention of configuration in the case of 3a- and 3 -aminocholesterol. 

Dinitrogen pentoxide (generated by mixing streams of dinitrogen tetroxide and ozonized oxygen) allowed to react countercurrently with 1-octanol, which is added dropwise at the top of a glass-spiraled reaction column, then quenched immediately with water -> octyl nitrate (Conversion 93%) added to hexamethyl-phosphoramide followed by Na-nitrite and ethyl malonate as nitrous acid scavenger, then stirred 1 hr. at 45° 1-nitrooctane (Y 95% conversion 41%). F. e. s. G. B. Bachman and N. W. Connon, J. Org. Chem. 34, 4121 (1969). 

Additives can be incorporated to improve the quality of diesel fuel. For example, ethyl nitrite, ethyl nitrate, and isoamyl nitrite when added to an oil will increase its CN value. The addition of 2.5% by volume of amyl nitrite to a diesel oil (CN = 26) increased the CN to 44. Additives such as amyl nitrate (C5H11ONO2) when added at about 0.1 % by volume will increase the CN by 4, and 0.25% will add 7 to the CN of the fuel. Other nitrates such as heptyl and octyl nitrates are also ignition improvers. A similar effect is obtained when ammonium nitrate is added to oil. A 2% by weight addition of a solution of 5 M NH4NO3 in water can increase the CN of a diesel fuel from 39 to 42. Other additives will prevent gum formation, decrease surface tension permitting a finer spray, or reduce the change in fuel properties due to changes in temperature. 

Note 4—In diesel fuel, the presence of alkyl nitrates such as amyl nitrate, hexyl nitrate, or octyl nitrate causes a higher residue value tlum observed in untreated fuel, which can lead to erroneous conclusions as to the coke forming propensity of the fuel. The presence of alkyl nitrate in the fUel can be detected by Test Method D 4046. 

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