Amide group, chlorination

Thus, to achieve mirror-symmetric or centrosymmetric cyclobutane derivatives, one would start with monomers that are substituted with dichloro groups or amide functions, respectively. Both the chlorines and the amide groups can subsequently be removed readily, without affecting the stereochemistry of the ring. 

Many of the chiral molecules containing amide groups were bonded to a solid support for the preparation of CSPs [16-19]. The racemic compounds resolved on these CSPs include a-hydroxycarbonyls, /i-hydroxycarbonyls, amino acids, amino alcohols, amine, and derivatized and underivatized diols. The preliminary chiral diamide phase [(/V-foriuyl-L-valyl)aminopropyl)silica gel] has sufficient separability for racemic /Y-acylatcd a-amino acid esters but not in other types of enantiomer [16]. Most of the eluents used with these CSPs are of normal phase mode, including w-hcxanc, 2-propanol, chlorinated organic solvents, and acetonitrile. 

Fig. 2. Structure of the ochratoxins. These metaholites form different classes depending on the nature of the amide group (a-c), and the presence or absence of a chlorine moiety at in the phenyl. 

The biochemical mode of action of dalapon has not been unequivocally elucidated. The protein precipitating action of chlorinated aliphatic acids, hence of dalapon, is known (Redemann and Hamaker, 1954), and it has also been proved by the investigations of Kemp et al. (1969) that the acid form of dalapon is able to form a hydrogen bond with the amide group of the protein molecule, so that this mechanism, in blocking enzyme activity, may be the cause of the phytotoxic action. Hilton et al. (1959) proved that dalapon inhibits the pantothenic acid synthesis of plants. 

Four polymers with different surface compositions were used in this study—polystyrene (PS), poly(methyl methacrylate) (PMMA), polyacrylamide (PAM), and a poly(vinylidene chloride) (PVeC) copolymer (containing 20% polyacrylonitrile). Polystyrene has essentially a hydrocarbon surface, whereas the surfaces of poly (methyl methacrylate) and polyacrylamide contain ester and amide groups, respectively. The surface of the poly(vinylidene chloride) copolymer on the other hand will contain a relatively large number of chlorine atoms. The presence of acrylonitrile in the poly(vinylidene chloride) copolymer improved the solubility characteristics of the polymer for the purposes of this study, but did not appreciably alter, its critical surface tension of wetting. Values of y of these polymers ranged from 30 to 33 dynes per cm. for polystyrene to approximately 40 dynes per cm. for the poly(vinylidene chloride) copolymer. No attempt was made to determine e crystallinity of the polymer samples, or to correlate crystallinity with adsorption of the fluorocarbon additives. 

An early synthesis, published in 1983 and 1984 [83], requires three steps from 2-chloro-N-(2,4-dichlorophenyl)acetamide (Scheme 17.17). First, the amide group is transformed into imidoyl chloride with phosphorus pentachloride, followed by displacement of the two non-aromatic chlorine atoms by two equivalents of the potassium salt of 1,2,4-triazole. The triazolyl group borne by the imino bond being the best leaving group is replaced when reacted with a good nucleophile such as (4-chlorophenyl)methanethiol. The stereochemistry (E or Z) of the double bond is not stated in the literature. 

With one major target fully disassembled into four components of reasonable size, simplification of the remaining piece, tripeptide 18, was then achieved in just a few retrosynthetic operations, starting with the removal of its lone aryl chlorine substituent to afford 44 as delineated in Scheme 7. Subsequent removal of one peptide building block (45) from this fragment then revealed dipeptide 46, whose amide group could then be dissected into amine 47 and carboxylic acid 48. 

For detecting small amounts of this antibiotic on silica gel plates an N-chlorination of the amide group of chloramphenicol with chlorine vapor, evolving from the decomposition of calcium hypochlorite, followed by selective reduction of the excess chlorine with formaldehyde vapor, has been worked out (60). The solvent was ethyl acetate, the plate was dried, placed for 2 min into a tank with Ca(OCI)2, transferred to a tank with formalin (30-45 s), and sprayed with a solution containing 1% starch, 1% Kl, nd 0.05% Triton X-100. The purplish-blue spots (/ /= 0.61) give a low detection limit of 60 ng. 

Attempted chlorosulfonation of 5-benzylidenehydantoin, using a mixture of chlorosulfonic acid (three equivalents) in excess thionyl chloride, gave a mixture of products, possibly involving initial chlorination of the amide group. 

For example, water can be absorbed into nylon 6/6 by forming hydrogen bonds with the amide groups. At elevated temperatures nylon swells by water absorption. Low density polyethylene (LDPE) becomes increasingly susceptible to attack by aromatic, chlorinated and aliphatic hydrocarbons as the temperature is increased. Attack of LDPE by aliphatic hydrocarbons is an example of dispersion (non-polar) forces. 

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