Unpleasant

Isobutyric acid, dimethylacetic acid, 2-methylpropanoic acid, (CHjjjCH COOH, colourless syrupy liquid with an unpleasant odour b.p. 154°C. Prepared by oxidation of 2-methylpropanol with K2Cr207 and H2SO4. Salts soluble in water. Used in alkaline solution for sweetening gasoline. 

C. The only lerpene-like natural hydrocarbon containing nine C atoms. It is found in East Indian sandalwood oil and also in Siberian, German and Swedish pine-needle oils. It has a rather unpleasant smell, resinifies easily and is difficult to obtain pure. 

QHgNiOiS. Colourless crystals, m.p. 164 5-166-5" C. It is usually prepared by treating p-acetamidobenzenesulphonyl chloride with ammonia, and hydrolysing the acetyl derivative to the base. Used for the treatment of streptococcal infections, gonorrhoea, meningococcal meningitis and urinary infections. Liable to cause unpleasant reactions, such as nausea, cyanosis and skin rashes. 

Isovaleric acid, Me2CHCH2COOH, is a colourless liquid with the unpleasant odour of valerian, b.p. 177 "C. Occurs in the roots of valerian and angelica together with an optically active form of methylethylethanoic acid. Prepared by oxidation of isoamyl alcohol. A mixture of acids similar to that obtained from valerian roots is prepared by oxidation of fusel oil. 

A knowledge of these compounds is important because they often have undesirable attributes, e.g., unpleasant odor, the SO2 formed by combustion, catalyst poisoning. There are a number of refining processes to eliminate sulfur compounds. 

There is no reliable standard method to characterize odor and specifications often indicate merely a not-unpleasant odor . 

Carbon disulphide is a volatile, evil-smelling liquid, although if carefully purified, the unpleasant smell is removed, as it is due to impurity. The vapour is inflammable and can form explosive mixtures in air ... 

Phosphine is a colourless gas at room temperature, boiling point 183K. with an unpleasant odour it is extremely poisonous. Like ammonia, phosphine has an essentially tetrahedral structure with one position occupied by a lone pair of electrons. Phosphorus, however, is a larger atom than nitrogen and the lone pair of electrons on the phosphorus are much less concentrated in space. Thus phosphine has a very much smaller dipole moment than ammonia. Hence phosphine is not associated (like ammonia) in the liquid state (see data in Table 9.2) and it is only sparingly soluble in water. 

All Group VI elements form a hydride HjX. With the notable exception of water, they are all poisonous gases with very unpleasant smells. Table 10.2 gives some of their important physical properties. 

Hydrogen sulphide is a colourless gas, b.p. 213 K, with a most unpleasant odour the gas is very toxic, but the intense odour fortunately permits very minute concentrations of the gas to be detected. 

Liquid chlorine dioxide, ClOj, boils at 284 K to give an orange-yellow gas. A very reactive compound, it decomposes readily and violently into its constituents. It is a powerful oxidising agent which has recently found favour as a commercial oxidising agent and as a bleach for wood pulp and flour. In addition, it is used in water sterilisation where, unlike chlorine, it does not produce an unpleasant taste. It is produced when potassium chlorate(V) is treated with concentrated sulphuric acid, the reaction being essentially a disproportionation of chloric(V) acid ... 

Ethylene when deeply inhaled produces temporary anaesthesia which is almost devoid of unpleasant after-effects hence it has been used for dental surgery, minor operations, etc. 

The top of the bench should always be kept clean and dry this can easily be done if a wet and a dry rag are kept at hand. Apparatus not immediately required (a) should be kept as far as possible in a cupboard beneath the bench if it must be placed on the bench, it should be arranged in a neat and orderly manner. All apparatus should be washed immediately after use and placed in a position to drain at the first opportunity, the apparatus should be dried. It must be emphasised that as a general rule a deposit of dirt or tar is more easily removed when it is freshly formed a suitable cleaning agent can usually be found while one still remembers the nature of the material or the circumstances attending its formation. It is hardly necessary to add that sohd waste and filter papers must not be thrown into the sink, and that all operations requiring the handhng of unpleasant and noxious materials sliould be carried out in the fume cupboard ( hood ). 

CAUTION. Bromine must be handled with great care and in the fume cupboard. The liquid produces painful bums and the vapour is unpleasant. Bromine bums should be treated immediately with a liberal quantity of glycerine. If the vapour is inhaled, relief may be obtained by soaking a handkerchief in alcohol and holding it near the nose. 

It is important not to allow the reaction mixture to become appreciably alkaline, since the free base then decomposes rapidly yielding benzyl mercaptan, which has an unpleasant odour. 

The acetamide often contains a minute amount of impurity having an odour resembling mice excrement this can be removed by washing with a small volume of a 10 per cent, solution of ethyl alcohol in ether or by recrystallLsation. Dissolve 5 g. of impure acetamide in a mixture of 5 ml. of benzene and 1 5 ml. of dry ethyl acetate warm on a water bath until all is dissolved and cool rapidly in ice or cold water. Filter oflF the crystals, press between Alter paper and dry in a desiccator. The unpleasant odour is absent and the pure acetamide melts at 81°. Beautiful large crystals may be obtained by dissolving the acetamide (5 g.) in warm methyl alcohol (4 ml.), adding ether (40 ml.) and allowing to stand. 

Dissolve 180 g. of commercial ammonium carbonate in 150 ml. of warm water (40-50°) in a 700 ml. flask. Cool to room temperature and add 200 ml. of concentrated ammonia solution (sp. gr. 0 88). Introduce slowly, with swirling of the contents of the flask, a solution of 50 g. of chloroacetic acid (Section 111,125) in 50 ml. of water [CAUTION do not allow chloroacetic acid to come into contact with the skin as unpleasant burns will result]. Close the flask with a solid rubber stopper and fix a thin copper wire to hold the stopper in place do not moisten the portion of the stopper in contact with the glass as this lubrication will cause the stopper to slide out of the flask. Allow the flask to stand for 24-48 hours at room temperature. Transfer the mixture to a distilling flask and distil in a closed apparatus until the volume is reduced to 100-110 ml. A convenient arrangement is to insert a drawn-out capillary tube into the flask, attach a Liebig s condenser, the lower end of which fits into a filter flask (compare Fig.//, 1) and connect the... 

Mercaptans RSH (also thioethers or sulphides R SR and disulphides R SSR") are generally hquids and possess unpleasant odours. 

CAUTION. Phenylhydrazine is highly poisonous and produces unpleasant bums in contact with the skin. Wash off immediately any liquid which has come into contact with the skin first with 2 per cent, acetic acid, then with soap and water. 

This preparation must be carried out in the fume cupboard since thiophenol has an extremely unpleasant and repulsive odour the sub-stance should not be allowed to come into contact with the hands or clothing since the odour clings for days. 

The deliquescent solid must be stored in a dry, tightly-stoppered container. If exposed to the air it deteriorates rapidly, developing an unpleasant odour. Samples that have been kept for some time are best recrystallised from absolute ethanol before use. 

Chloroform - a very common solvent which has a rather unpleasant smell. Try not to get too close to this stuff as it has anaesthetic properties which you don t really want to find out about. 

Detergents are designed to be effective in hard water meaning water containing calcium salts that form insoluble calcium carboxylates with soaps These precipitates rob the soap of Its cleansing power and form an unpleasant scum The calcium salts of synthetic deter gents such as sodium lauryl sulfate however are soluble and retain their micelle forming ability even m hard water... 

A collection of physical prop erties of some representative amines is given in Appendix 1 Most commonly encoun tered alkylamines are liquids with unpleasant fishy odors... 

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