Paraldehyde, preparation

On acetylation it gives acetanilide. Nitrated with some decomposition to a mixture of 2-and 4-nitroanilines. It is basic and gives water-soluble salts with mineral acids. Heating aniline sulphate at 190 C gives sulphanilic add. When heated with alkyl chlorides or aliphatic alcohols mono- and di-alkyl derivatives are obtained, e.g. dimethylaniline. Treatment with trichloroethylene gives phenylglycine. With glycerol and sulphuric acid (Skraup s reaction) quinoline is obtained, while quinaldine can be prepared by the reaction between aniline, paraldehyde and hydrochloric acid. 

The acetaldehyde should be freshly distilled (b.p. 20-5-21°). It can be conveniently prepared by depolymerising pure dry paraldehyde (see Section 111,65). 

Examples include acetaldehyde, CH CHO paraldehyde, (CH CHO) glyoxal, OCH—CHO and furfural. The reaction is usually kept on the acid side to minimize aldol formation. Furfural resins, however, are prepared with alkaline catalysts because furfural self-condenses under acid conditions to form a gel. 

Broirjal has been prepared by brominating a solution of paraldehyde in ethyl acetate, and by passing bromine vapor through absolute alcohol. ... 

Tetrahydroharman, m.p. 179-80°, has been prepared by a number of workers by a modification of this reaction, viz., by the interaction of tryptamine (3-)5-aminoethylindole) with acetaldehyde or paraldehyde and Hahn et al. have obtained a series of derivatives of tetrahydronorharman by the use of other aldehydes and a-ketonic acids under biological conditions of pH and temperature, while Asahina and Osada, by the action of aromatic acid chlorides on the same amine, have prepared a series of amides from which the corresponding substituted dihydronorharmans have been made by effecting ring closure with phosphorus pentoxide in xylene solution. 

Paraldehyde, a sedative and hypnotic agent, is prepared by treatment of acetaldehyde with an acidic catalyst. Propose a mechanism for the reaction. 

Butyrchloral has been prepared by chlorination of acetaldehyde 2 and of paraldehyde. Butyrchloral hydrate has been prepared by treatment of a,j8-dichlorobutyraldehyde with chlorine and water.3 Butyrchloral has also been prepared4 by treatment of crotonaldehyde with hydrogen chloride followed by chlorination. Brown and Plump have used a procedure similar to the one described here.3... 

Pure formaldehyde, prepared by vacuum depolymerisation of paraldehyde, was collected as a solid at — 189°C. When the flask was transferred to a Cardice-ethanol bath, the contents began to repolymerise exothermally and ignited. 

The procedure given above is essentially a large-scale adaptation of that of Filachione.2 Bromoacetal has been prepared by the bromination of acetal directly,3 or in the presence of calcium carbonate 4 by action of sodium ethoxide on a,/3-dibromodiethyl ether by bromination of paraldehyde followed by action of ethyl alcohol 6 and by the action of ethyl alcohol on bromoacetal-dehyde.7... 

Like paraldehyde, metaldehyde can be preserved, and, when freshly prepared, is odourless. It also has no aldehydic properties. On keeping, however, a distinct odour of acetaldehyde becomes evident —a sign that here also an equilibrium is slowly being established. Metaldehyde can be completely depolymerised by heating. Molecular weight determinations (in phenol) show that metaldehyde is tetra-molecular (Hantzsch) the examination of the space lattice of crystals by the method of Laue and Bragg points to the same conclusion (Mark). 

Alcohol. Along with several bromide preparations and paraldehyde, alcohol has often been used to relieve anxiety. Due to the marked untoward social and medical consequences of frequent use, alcohol has no place in the treatment of anxiety. Unfortunately, the inappropriate use of alcohol to self-medicate anxiety, depression, insomnia, or other symptoms often leads to alcoholism and therefore contributes to a signihcant public health problem. 

Sulfuric acid cannot be used for the synthesis of acetals and so bis(2,2-dinitropropyl)acetal (179) is prepared from the reaction of paraldehyde with 2,2-dinitropropanol (25) in the presence of boron trifluoride.333 323 50 50 eutectic mixture of bis(2,2-dinitropropyl)formal (175) and bis(2,2-dinitropropyl)acetal (179) has found use as an energetic liquid plastisizer for nitrocellulose. 

Severe myocardial disease or coronary occlusion psychoses hypersensitivity to disulfiram or to other thiuram derivatives used in pesticides and rubber vulcanization patients receiving or who have recently received metronidazole, paraldehyde, alcohol, or alcohol-containing preparations. 

After 3 5 g of the hypnotic paraldehyde a qualitatively similar pattern of action was observed as with alcohol, although the stimulation phase was briefer and less pronounced and the paralysing action of the preparation was stronger. Following the intake of chloral hydrate and with the inhalation poisons the paralysing effect was still more pronounced. 

Ethyl-3-methylpyridine (also known as aldehyde-collidine ) has been prepared by heating aldehyde-ammonia aldehyde-ammonia and acetaldehyde or paraldehyde aldol-ammonia and ammonia paraldehyde and ammonia <> 11,12 acetamide,1 or acetamide and phosphorus pentoxide ethylene glycol and ammonium chloride ethylidene chloride or bromide and ammonia ethylidene chloride and acetamide, ethylamine, or n-amylamine crotonic acid and a calcium chloride-ammonia complex 1 and by passage of acetylene or acetaldehyde and ammonia over alumina and other catalysts. 

The acetaldehyde may be prepared conveniently by depo-lymerizing pure, dry paraldehyde with tolucnesulfonic acid as a catalyst. Acetaldehyde boiling at 20.5-21° must be used for this preparation. 

Fulminate can be prepared from acetaldehyde instead of from alcohol, and from substances which are convertible into acetaldehyde, such as paraldehyde, metaldehyde, dimethyl- and diethyl-acetal. Methyl alcohol, formaldehyde, propyl alcohol, butyralde-hyde, glycol, and glyoxal do not yield fulminate. ... 

When cyclopentanecarbaldehyde is prepared, it is a colourless liquid. On standing, particularly with traces of acid, it forms the crystalline trimer. The trimer is a stable six-membered heterocycle with all substituents equatorial Acetaldehyde (ethanal) forms a liquid trimer called paraldehyde , which reverts to the monomer on distillation with catalytic acid. More interesting is metaldehyde , the common slug poison, which is an all-as tetramer (2,4,6,8-tetramethyl-l,3,5,7-tetroxocane) formed from acetaldehyde with dry HC1 at below 0°C. Metaldehyde is a white crystalline solid that has all the methyl groups pseudoequatorial, and it reverts to acetaldehyde on heating. 

Acetaldehyde may be conveniently prepared by distilling from paraldehyde in the presence of a trace of sulfuric add an efficient fractionating column should be used. 

Of all the women chemists, Phyllis Violet McKie24 of the University College of Wales, Bangor, one of Orton s protegees, seems to have been the most productive during the war period. McKie was part of the team at Bangor producing paraldehyde.25 In addition, she devised a new method for the preparation of the explosive tetranitromethane for the Ministry of Munitions, and she studied methods of preparation of saccharin and vanillin for war purposes.26 Orton reported back to the War Committee ... 

Simple saturated and olefinic aldehydes condense with ammonia to give alkylpytidines (Chichibabin), but the products are frequently complex mixtures from which pure compounds are separated with difficulty. An exception is the preparation of 5-ethyl-2-methylpyridine in 53% yield from paraldehyde and ammonium hydroxide. In an extensive study of the reaction, it has been pointed out that other single products can sometimes be obtained in fair yields by proper choice of reagents and conditions. ... 

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