Trichloroacetaldehyde = chloral

Trichloroacetaldehyde (chloral) reacts with glucose in the presence of sulfuric acid to form two monoacetals and four diacetals. The trichloro acetal is cleaved by reduction (H2, Raney Ni, 50% NaOH, EtOH, 15 min). The trichloro acetal can probably be cleaved with Zn/AcOH [cf. ROCH(R )OCH2CCl3 cleaved by Zn/ AcOH, AcONa, 20°, 3 h, 90% yield ]. 

Trichloroacetaldehyde (chloral) reacts with glucose in the presence of sulfuric acid to form two mono- and four diacetals. ... 

When dissolved in water, trichloroacetaldehyde (chloral, CCJ3CHO) exists primarily as chloral hydrate, CCl CHCOH, better known as "knockout drops." Show the structure of chloral hydrate. 

Newman LM, LP Wackett (1991) Fate of 2,2,2-trichloroacetaldehyde (chloral hydrate) produced during trichloroethylene oxidation by methanotrophs. Appl Environ Microbiol 57 2399-2402. 

If there is a suitable electron-withdrawing substituent, hydrate formation may be favoured. Such a situation exists with trichloroacetaldehyde (chloral). Three chlorine substituents set up a powerful negative inductive effect, thereby increasing the 8- - charge on the carbonyl carbon and favouring nucleophilic attack. Hydrate formation is favoured, to the extent that chloral hydrate is a stable solid, with a history of use as a sedative. 

Addition of trichloroacetaldehyde (chloral) to benzene in the presence of aluminum chloride [160]. 

Trichloroacetaldehyde (chloral) reacts with sulfur tetrafluoride with a Cl-F shift. At 150 C... 

Studies on complexes of higher aldehydes with starch were performed with a view to preserving natural food aromas. Among aldehydes, only trichloroacetaldehyde (chloral) has been studied extensively as a coacervant... 

Asymmetric anionic polymerization can convert trichloroacetaldehyde (chloral) to a one-handed helical, isotactic polymer (44) having a 4/1-helical conformation with high optical activity ([oi]d +4000° in film).28114-118 Anionic initiators such as 45,115 46,115 and 47117 and Li salts of optically active carboxylic acids or alcohols are used for the polymerization. Although the polymers are insoluble in solvents and their conformation in solution cannot be directly... 

In the reaction of acetaldehyde with dichlorine (Equation 4.16), hydrogen atoms are substituted for chlorine atoms to give mono-, di-, and trichloroacetaldehyde (chloral) chlorine does not displace the oxygen atoms. 

Trichloroacetaldehyde (chloral), b.p. 97.8°/760 mm, is formed on chlorination of ethanol with irradiation and stirring. Absolute ethanol is no longer used, as in Liebig s procedure,624 but, instead, aqueous 70-80% ethanol which leads directly to chloral hydrate ... 

Chlorinatioii of EAanoL Chloral Either 95 per cent or absolute ethyl alcohol can be chlorinated to produce trichloroacetaldehyde (chloral) through a series of reactions frequently represented as follows ... 

With most other aldehydes or ketones, however, the hydrates cannot be isolated because they readily lose water to reform the carbonyl compound that is, the equilibrium constant (Sec. 3.11) is less than 1. An exception is trichloroacetaldehyde (chloral), which forms a stable crystalline hydrate, CCl3CH(OH)2. Chloral hydrate is used in medicine as a sedative and in veterinary medicine as a narcotic and anesthetic for horses, cattle, swine, and poultry. The potent drink known as a Mickey Finn is a combination of alcohol and chloral hydrate. 

Finally, in this vein, and as noted earlier for electrophilic substitution in alkyl-substituted arenes, a variety of substitutions can be effected. Among these is the Friedel-Crafts-type acylation of chlorobenzene (CeHsCl) by 2,2,2-trichloroethanal (trichloroacetaldehyde, chloral [CCI3CHO]), which, as shown in Scheme 7.15, results in the formation of l,l,l-trichloro-2-[di(p-chlorophenyl)]ethane (dichlorodiphenyl-trichloroethane [DDT]). 

TTie first item in Table 9.3 is simply the familiar hydration (see, e.g., Rgure 8.4) of aldehydes and ketones. As previously discussed, these geminal diols are normally in equilibrium with the corresponding carbonyl (C=0) compound and, with few exceptions (e.g., methanal [formaldehyde, H2CO] 2,2,2-trichloroacetaldehyde [chloral, CI3CCHO], see Chapter 8), the equilibrium lies far on the side of the aldehyde or ketone. The same general ideas obtain with regard to the next three items in Table 9.3, except that hemiacetals and hemiketals in cyclic systems (e.g., carbohydrates, Chapter 11), are more common than their open chain forms. 

---