1 - 6- hexyl

The additives for improving the cetane number, called pro-cetane, are particularly unstable oxidants, the decomposition of which generates free radicals and favors auto-ignition. Two families of organic compounds have been tested the peroxides and the nitrates. The latter are practically the only ones being used, because of a better compromise between cost-effectiveness and ease of utilization. The most common are the alkyl nitrates, more specifically the 2-ethyl-hexyl nitrate. Figure 5.12 gives an example of the... 

Unlike spark-induced combustion engines requiring fuel that resists autoignition, diesel engines require motor fuels, for vhich the reference compound is cetane, that are capable of auto-igniting easily. Additives improving the cetane number will promote the oxidation of paraffins. The only compound used is ethyl-2-hexyl nitrate. 

Fig. Ill-IS. Surface tension data for aqueous alcohol illustration of the use of the Gibbs equation. (1) -butyl (2) -amyl (3) -hexyl (4) -heptyl (5) -octyl. (Data from Ref. 126).

Octan-2-ol (A), sometimes called sec.octy alcohol, can be obtained, at a low price and of high purity, from technical sources. As a secondary alcohol, it can be readily oxidised by potassium dichromate-sulphuric acid to n-hexyl... 

Place 80 g, of hydroxylamine sulphate (or 68-5 g. of the hydrochloride), 25 g. of hydrated sodium acetate, and 100 ml. of water in a 500 ml. flask fitted with a stirrer and a reflux water-condenser, and heat the stirred solution to 55-60°. Run in 35 g (42 nil,) of -hexyl methyl ketone, and continue the heating and vigorous stirring for ij hours. (The mixture can conveniently be set aside overnight after this stage.) Extract the oily oxime from the cold mixture twice with ether. Wash the united ethereal extract once with a small quantity of water, and dry it with sodium sulphate. Then distil off the ether from the filtered extract, preferably using a distillation flask of type shown in Fig. 41 (p. 65) and of ca, 50 ml, capacity, the extract being run in as fast as the ether distils, and then fractionally distil the oxime at water-pump pressure. Collect the liquid ketoxime, b.p. 110-111713 mm. Yield, 30-32 g. 

This preparation illustrates the preparation of a liquid hydrocarbon from a Grignard reagent. The Grignard reagent from n-hexyl bromide may be decomposed either with dilute sulphuric acid or with solid ammonium chloride the latter gives a somewhat better 3neld. 

Prepare a Grignard reagent from 24 -5 g. of magnesium turnings, 179 g. (157 ml.) of n-heptyl bromide (Section 111,37), and 300 ml. of di-n-butyl ether (1). Cool the solution to 0° and, with vigorous stirring, add an excess of ethylene oxide. Maintain the temperature at 0° for 1 hour after the ethylene oxide has been introduced, then allow the temperature to rise to 40° and maintain the mixture at this temperature for 1 hour. Finally heat the mixture on a water bath for 2 hours. Decompose the addition product and isolate the alcohol according to the procedure for n-hexyl alcohol (Section 111,18) the addition of benzene is unnecessary. Collect the n-nonyl alcohol at 95-100°/12 mm. The yield is 95 g. 

Primary alcohols, lower than hexyl, dissolve there may be some darkening, but the solution remains clear. 

Primary alcohols, hexyl and higher, do not dissolve appreciably the aqueous phase remains clear. 

Place 179 g. (109-5 ml.) of redistilled thionyl chloride in the 250 ml. Claisen flask and 51 g. (62-6 ml.) of n-hcxyl alcohol, b.p. 156-158°, in the separatory funnel. Add the nr-hexyl alcohol during 2 hours there is a slight evolution of heat, sulphur dioxide is evolved (hence carry out the... 

Nitro-n-hexane. Use 41 g. of dry silver nitrite, 51 g. of n-hexyl iodide (35-5 ml.) and 100 ml. of sodium dried ether. Reflux on a water bath for 8 hours decant the ethereal solution and wash the sohd well with sodium dried ether. Distil the residue, after the removal of the ether from the combined extracts, from 5 g. of dry silver nitrite, and collect the fraction of b.p. 190-192° (13 g.) as 1-nitro -hexane. The pure compound is obtained by distilling under diminished pressure b.p. 81 6°/15 mm. 

Di-n-hexyl ether. Use 50 g. (61 ml.) of n-hexyl alcohol (b.p. 156-157°) and 6 g. (3-5 ml.) of concentrated sulphuric acid, and heat until the temperature rises to 180°. Pour the reaction mixture into water, separate the upper layer, wash it twice with 5 per cent, sodium hydroxide solution, then with water, and dry over anhydrous potassium carbonate. Distil from a 50 ml. Claisen flask, and collect the fractions of b.p. (i) 160-221° (17 g.), and (u) 221-223° (17 g.). Reflux fraction (i) with 4 g. of sodium and distil from the excess of sodium 9 - 5 g. of fairly prure n-hexyl ether, fraction (iii), are thus obtained. Combine fractions (ii) and (iii) and distil from a little sodium collect the pure n-hexyl ether (19 g.) at 221 - 5-223°. 

Place 204 g. (249-5 ml.) (2 gram mols) of dry n-hexyl alcohol in a 350 ml. Claisen flask with fractionating side arm. Introduce 5-75 g. (0-25 gram atoms) of clean sodium in small pieces and warm under reflux (as in Fig. Ill, 58, 1 but with dropping funnel omitted ) until all the sodium has reacted (ca. 2 hours). Introduce 39 g. (20 ml.) (0-25 gram... 

Finally distil from a well-lagged Widmer flask (compare Figs. II, 24, 2-5) over a little sodium. Collect the cycZo hexyl ethyl ether at 148-150°. The yield is 21 g. If the sodium is appreciably attacked, repeat the distillation from a fresh quantity of sodium. 

---