Alcohols as Impurities

In this reaction, the presence of active hydrogen compounds (HX), such as water and alcohols as impurities, is required, and alcohols produced by Eqs. (1) and (2) accelerate the curing reaction (cf., e.g., Smith 9) and Kakurai U)). Different mechanisms have been proposed by Smith 9), Tanaka U), and Bell12), but they have not yet been confirmed. 

Along with the desired main product, industrial ethoxylated alcohols contain some quantity of initial alcohol as impurity, especially at low m, and free PEG the amount of which increases with m. Ethoxylated alcohols represent mixtures of oligomer-homologues with a wide ethylene oxide chain length distribution. Hence m is always some average value. 

One cc. of the unknown is treated cautiously with 1 cc. of acetyl chloride. The signs of reaction are the evolution of heat, the liberation of hydrochloric acid gas, and the formation of an ester. The fact that esterification has taken place is indicated by the odor of the reaction product after it has been poured into a small amount of water to remove the excess of acetyl chloride a mere trace of alcohol as impurity in an ether might also be respon-... 

The reaction with sodium is by no means an infallible practical test for alcohols since, strictly speaking, it is applicable only to pure anhydrous liquids. Traces of water, present as impurities, would give an initial evolution of hydrogen, but reaction would stop after a time if an alcohol is absent furthermore, certain esters and ketones also evolve hydrogen when treated with sodium (compare Section XI,7,6). It may, however, be assumed that if no hydrogen is evolved in the test, the substance is not an alcohol. 

Alcohol sulfates commonly have free alcohol and electrolytes as impurities. Other hydrophobic impurities can also be present. A method suitable for the purification of surfactants has been proposed by Rosen [120]. Consequently, commercial products have CMCs that deviate from the accepted reference values. This was demonstrated by Vijayendran [121] who studied several commercial sodium lauryl sulfates of high purity. The CMC was determined both by the conductimetric method and by the surface tension method. The values found were similar for both methods but while three samples gave CMC values of 7.9, 7.8, and 7.4 mM, close to the standard range of 8.0-8.2 mM, three other samples gave values of 4.1, 3.1, and 1.7 mM. The sample with a CMC of 7.9 mM was found to have a CMC of 8.0 mM with no detectable surface tension minima after purification and recrystallization. This procedure failed in all other cases. 

Note Commerially available allyl alcohol may contain allyl chloride, 1-propanol and propanal as impurities. 

Excellent yields can be obtained when the mixture of RC=CLi and the epoxide in ammonia is allowed to stand for 12 to 24 hours [2]. With sodium acetylides, there is some risk of subsequent attack of the acetylenic alcoholate on the epoxide, especially when the latter compound is used in excess. The reaction of acetylenic magnesium halides, RCsCMgX, with epoxides also leads to homopropargylic alcohols, but this is generally not recommended as a satisfactory method, as impure products are often obtained [62], Coordination of the epoxide-oxygen atom with the Lewis acid may give rise to a Sjql-like attack of RCaC on... 

The total yield of crude centrifuged methylamine hydrochloride is 830-850 g. This product contains, as impurities, water, ammonium chloride, and some dimethylamine hydrochloride. In order to obtain a pure product, the crude methylamine hydrochloride is recrystallized from absolute alcohol (Note 4). The crude salt is placed in a 5-I. round-bottom flask fitted with a reflux condenser protected at the top with a calcium chloride tube 2 1. of absolute alcohol is added and the mixture heated to boiling. After about half an hour the undissolved material is allowed to settle and the clear solution is poured off. When the alcoholic solution is cooled, methylamine hydrochloride crystallizes out. It is filtered off and centrifuged, and the alcohol used for another extraction. The process is repeated until the alcohol dissolves no more of the product (about five extractions are necessary). In the flask 100-150 g. of ammonium chloride remains, making the total recovery of ammonium chloride 850-950 g. The yield of recrystallized methylamine hydrochloride is 600-750 g. (45-51 per cent of the theoretical amount, based on the ammonium chloride used up in the process). 

Firstly, various side reactions result from impurities left in the diazonium tetrafluoroborate (water, sodium nitrite, washing solvents). As already discussed, residual water or alcohols (often used to wash the solid diazonium tetrafluoroborate after filtration) substitute the diazo group in an ionic process to produce phenols or alkoxyarenes as byproducts. Residual alcohol can also lead to arenes through a radical hydrodediazoniation process, especially when electron-withdrawing groups are present, as in 3-fluoro-2-methoxy-5-(methoxyearbonyl)benzenediazo-nium tetrafluoroborate (ArF/ArH 4 1)227 or in 2-methyl-5-nitrobenzenediazonium tetrafluoroborate.240 Such radical phenomena increase when sodium nitrite is present as impurity... 

The product is dissolved by gentle heating and the solution is then cooled to 0° or below for several hours. The material remaining in the mother liquor (about 30 per cent of the total) may be recovered as impure, oily oxime by evaporation of the alcohol. 

Chloroform purified by the salicylide process contains no alcohol or ethyl chloride as impurities. 

Note. (1) Osmium tetroxide is extremely irritating and toxic and constitutes a severe eye injury hazard. It may be purchased in sealed ampoules, e.g. 100 mg the solution in t-butyl alcohol must be prepared and dispensed in an efficient fume cupboard, with the added protection of gloves and goggles. This solution is reasonably stable (e.g. the decomposition after one month is about 20%), provided that no 2-methylprop-l-ene arising from the t-butyl alcohol is present as impurity. In the latter case formation of... 

Secondary alcohols are much different chemically than primary alcohols, such as natural alcohols. In addition, commercial secondary alcohols are prepared from both even and odd carbon-numbered n-paraffins and thus contain both even and odd carbon-numbered alcohols. Oxo alcohols are primary alcohols, as are natural alcohols. However, oxo alcohols contain from twenty to sixty percent branched chain alcohols and also contain both even and odd carbon-numbered homologs. Ziegler alcohols are very similar to natural alcohols. They are primary alcohols and are a mixture of only even carbon-numbered homologs. The major differences between Ziegler and natural alcohols are trace impurities present and the range of synthetic products, C -C30, available. 

This side reaction leads to the formation of branched alcohols as well as branched olefins. These impurities are dimeric and are about twice the average molecular weight as the product alcohols. 

Arsenic Acid leach liquors Tributyl phosphate or higher alcohol extractant removes arsenic as impurity from other metals... 

In all preparations involving the use of diglyme it is essential that it be free of alcohols which might introduce trialkoxyboranes as impurities in the alkyltin hydrides. The diglyme can be purified best by distilling it from LiAlH4. Because this procedure can be hazardous unless properly done, the procedure outlined below is recommended. It is suggested that quantities be kept small (50 ml.) as a safety precaution. 

Dialkyl alkylphosphonates are of interest as analytes for a number of reasons. They may be present as impurities in nerve agents, and as such may be useful indicators of use or production as they are much more stable in the environment an example is diisopropyl methylphosphonate found in sarin. Dialkyl methylphosphonates may be formed in decontamination reactions of nerve agents in basic formulations containing alcohols or cellusolves. They are also important precursors to nerve agents, for example, dialkyl methylphosphonates are converted to the key... 

The residue left after the solvent - alcohol (in the earlier crystallization method) or xylene (from the washing technique) - has been distilled off, is a semi-solid substance consisting of a- trinitrotoluene, its isomers, dim trot oluenes and other nitro compounds, all of them found as impurities in TNT. 

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