Lachrymatory compound

Above 100 C a vigorous reaction resulting in the formation of tars and a lachrymatory compound (possibly BrCH2CH=0) may set in. 

HC=CCH=CHCH2Br, b.p. 40 C/15 mmHg, nD(20 ) 1.5350 (E.Z -85 15), is obtained in -70% yield by a similar procedure from the corresponding alcohol (p. 64). During the addition of PBr3 the solution turns very dark. The enyne bromide is a very lachrymatory compound. Contact of the liquid or vapour with the skin has a similar effect as in the case of propargyl bromide and other acetylenic bromides. 

Dibromobutyne is a skin-irritating and lachrymatory compound use protective gloves of suitable quality the experiment should be carried out in a well-ventilated hood. 

The answer to all these questions is found in the demonstration (37) that the monomeric, unstable, lachrymatory compound produced by onions is not 1-propenylsulfenic acid, the presumed precursor of the dimer, but, as suggested a decade earlier (38), thiopropionaldehyde-S-oxide (CH CHoCHSO). The mass spectographic evidence which suggested the sulfenic acid structure (22) for this product is consistent with the latter structure. The nuclear magnetic resonance and infrared spectral evidence are consistent only with it. A hypothesis uniting all the evidence is that the true product of the enzymatic reaction is the sulfenic acid, as... 

Nacconate 100 A lachrymatory liquid b.p. 25l°C. Manufactured from phosgene and 2,4-diaminotoJuene. Used for preparing polyurethane foams and other elastomers by reaction with polyhydroxy compounds. Produces skin irritation and causes allergic eczema and bronchial asthma. 

Redistilled commercial chloroacetone, b.p. 118-120°, is used. The compound is lachrymatory. It is prepared inter alia by the chlorination of acetone in the cold. 

Note 1. The compound has lachrymatory properties and may cause blisters on the skin. 

Fluorophenyl isocyanate [1195-45-5] M 137.1, b 55°/8mm, n 1.514. Purify by repeated fractionation through an efficient column. If IR indicated that there is too much urea (in the presence of moisture the symmetrical urea is formed) then dissolve in dry EtOH-free CHCI3, filter, evaporate and distil. It is a pungent LACHRYMATORY liquid, [see Hardy J Chem Soc 2011 1934-, and Hickinbottom Reactions of Organic Compounds Longmans p. 493 1957.]... 

The compound is lachrymatory it quickly polymerizes to an amorphous glass at 20 X. 

Reaction of /V,/V-unsubstituted selenoureas 332 with methyl vinyl ketone in the presence of ferric chloride in refluxing ethanol gives 2-amino-5-(l -ethoxy)-1,3-selenazoles 335 <06H(68)2145>. This approach obviates the use of lachrymatory halo carbonyl compounds frequently utilized in the synthesis of 1,3-selenazoles. 

Thiazole and its derivatives are conventionally prepared from lachrymatory, a-halo-ketones and thioureas (or thioamides) by Hantzsch procedure [146]. In a marked improvement, Varma et al. have synthesized the title compounds by the simple reaction of in situ-generated a-tosyloxyketones, from arylmethyl ketones and [hydroxy(tosyl-oxy)iodo]benzene (HTIB), with thioamides in the presence of K 10 clay using micro-wave irradiation (Scheme 6.43) the process is solvent-free in both the steps [147]. 

B. a,a -Dibromodineopentyl Ketone. Caution The dibromoketone, a highly volatile compound with lachrymatory properties, is a skin irritant which may induce allergic effects. Therefore, steps B and C should be performed in a well-ventilated hood. Rubber gloves should be worn. 

The most important flavour compound in raw onions is thiopropanal-S-ox-ide, the lachrymatory factor [145,146]. Other important flavour compounds are 3,4-dimethyl-2,5-dioxo-2,5-dihydrothiophene and alkyl alkane thiosulfonates such as propyl methanethiosulfonate and propyl propanethiosulfonate with a distinct odour of freshly cut onions [35, 36, 147]. Various thiosulfinates that have a sharp and pungent odour may also contribute to the flavour of onions. These compounds, however, are rapidly decomposed to a mixture of alkyl and alkenyl monosulfides, disulfides and trisulfides (Scheme 7.3) of which dipropyl disulfide, methyl ( )-propenyl disulfide, propyl ( )-propenyl disulfide, dipropyl trisulfide and methyl propyl trisulfide are the most important contributors to the aroma of raw and cooked onions (Table 7.5, Fig. 7.6) [148-150]. Recently, 3-mercapto-2-methylpentan-l-ol was identified in raw and cooked onions eliciting intense meat broth, sweaty, onion and leek-like odours [142, 151]. 

Shallots Allium ascalonicum) are an allium wherein the bulb laterals separate into individual bulbs. Apparently, shallots do not develop a lachrymatory factor, such as thiopropanal-S-oxide upon maceration [35]. The major aroma constituents in shallots are similar to those found in A.cepa. In raw shallots, the most important aroma compounds appear to be dipropyl disulfide, propyl ( )-prope-nyl disulfide, methyl propyl trisulfide, dimethyl trisulfide and dipropyl trisulfide (Table 7.5, Fig. 7.6) [35, 152, 153]. 

One particular advantage of this method is that the lachrymatory 3-chlorovinyl ketones may be produced in situ by the acylation of an alkyne. This route has been further extended to the synthesis of azapyrylium salts from an alkyne and the imidoyl chloride (651) and to diazapyrylium compounds from nitriles (Scheme 258) (65CB334). 

These are respectively the 5-oxides and 5-dioxides of thiocarbonyl compounds. The lachrymatory factor of onions was shown to be (Z)- ... 

The reactions are carried out at room temperature, except in the case of 2-methyl-5-isopropyl-acetophenone, which requires heat. The products are nearly insoluble in ether, benzene, petroleum ether and carbon tetrachloride, but dissolve in water or alcohol with decomposition. They cannot be recrystallised and hence impurities are removed by washing first with benzene and then with ether. The compounds are more or less unstable, some commencing to decompose at once and others not showing marked decomposition for a period of two weeks. Decomposition gives a reddish sticky mass with a strong lachrymatory, action and an odour like that of chloro-ketones. The following table shows the substances which have been obtained. 

These compounds are lachrymatory and should be kept away from the eyes. 

Chlorotrimethylsilane (2.7 g, 25 mmol) (1) (CAUTION) is added to a solution of lithium bromide (1.74g, 20 mmol) in dry acetonitrile (20 ml) (2) with good stirring under a nitrogen atmosphere. Cinnamyl alcohol (1.34 g, 10 mmol) is then added and the reaction mixture heated under reflux for 12 hours. The progress of the reaction is monitored by t.l.c. on silica gel plates with hexane as the eluant. On completion of the reaction (12 hours), the reaction mixture is taken up in ether (50 ml), washed successively with water (2 x 25 ml), sodium hydrogen carbonate solution (10%, 50 ml) and finally brine, and dried over anhydrous sodium sulphate. Evaporation of the ether affords the pure bromide in 93 per cent yield. The product may be recrystallised from ethanol and has m.p. 31-32 °C CAUTION this compound is lachrymatory. 

Note. (1) This compound is lachrymatory and may be a skin irritant. 

Notes. (1) This compound is lachrymatory and also produces a burning sensation on the skin the latter is relieved by washing the affected parts with alcohol. 

SH or -CH =S=0 in crushed onion is also associated with both lachrymatory and tongue tearing (itchy ) sensations. Careful evaluations of these compounds by threshold... 

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