Derek Bryce-Smith

Lead Induced Disorders of Mentation in Children

Present typical body burdens of the cumulative neurotoxic pollutant lead are now believed to be some 100–1000 times greater than those in pre-technology man. The effects of these seriously elevated levels on brain development and function in children are reviewed. All such effects so far discovered are adverse, and in conjunction with social factors and defective nutrition they can act to prevent a childs mental development reaching his or her true genetic potential. Most aspects of mentation, except possibly mathematical ability, appear to suffer dose-related disturbance at levels now typical for urban children, but impaired intelligence and deficits in the normal inhibitory control of behaviour appear to be prominent. Lead intoxication is therefore a phenomenon relevant to such important problems as educational underachievement and anti-social conduct disorders of the hyperactivity type characterised by a deficiency of inhibitory function in the central nervous system.

Mechanism of the photochemical meta-cycloaddition of alknes to the benzene ring

Abstract The mechanism of photochemical meta -cycloaddition of alkenes to arenes is considered in the light of new observations concerning the effects of bulky substituents.

Photoreactions of halogenobenzenes with cyclopentene. Insertion into carbon–halogen bonds

Chloro-, bromo-, and iodo-benzenes photoreact with cyclopentene to give, principally, products derived from insertion into the C–halogen bond, a type of reaction hitherto unknown in this series, but fluorobenzene mainly forms meta- and para-cycloadducts with only a minor proportion of the cis-insertion product.

Photonucleophilic substitution in aryl fluorides: photochemical cine-substitution and evidence for an addition–elimination mechanism

Photosubstitution of aryl fluorides by primary and secondary amines can give both ‘normal’ and cine-substitution products, probably by an addition-elimination mechanism; ortho-type photoadducts are also produced in most cases, although p-difluorobenzene gives the para-adduct (6) with diethylamine.

The photoaddition of aliphatic amines to benzene

Primary, secondary, and tertiary aliphatic amines undergo photoaddition to benzene via photoexcitation of benzene to the S1 state. Primary amines give products of 1,2-, 1,3-, and 1,4-addition of the N–H bond, although the 1,3-adducts are derived from secondary photoreactions of the 1,2-adducts by way of hexa-1,3,5-triene intermediates. Secondary amines react similarly, but give only 1,2- and 1,4-adducts. The photoadditions of tertiary amines involve an α-C–H bond in the amine and occur 1,4- to the benzene ring, but little addition occurs in the absence of methanol or other proton donors. The mechanisms of these reactions have been investigated, and the findings are discussed : charge-transfer processes and both polar and radical intermediates appear to be involved.

Organo-mercury-(I) and -(II) ketenide derivatives

Reactions of certain mercury-(I) and -(II) salts with keten or acetic anhydride yield organometallic ketenide derivatives of mercury-(I) and -(II) respectively: the former represent the first examples of stable organo-mercury(I) compounds to be characterised.

Preparation, properties and structure of crystalline silver ketenide (µ-oxoethenylidene disilver) and its pyridine complex

Silver ketenide of empirical formula Ag2CCO is obtained by direct reaction of ketene or an in situ source of ketene such as acetic anhydride, isopropenyl acetate, vinyl acetate or phenyl acetate with certain silver salts, normally in the presence of a base.

Thermal cycloaddition of N-arylmaleimides to phenols: the convenient synthesis of bicyclo[2.2.2]oct-2-en-5-one and tricyclo[3.3.0.02,8]octan-2-one derivatives from phenols

Monohydric phenols undergo 2,5-thermal cycloaddition of N-substituted maleimides to give bicyclo[2.2.2]oct-2-en-5-ones. Homopolymers of the maleimides are also concurrently formed, except in the case of N-(2,6-dimethylphenyl)maleimide: this is the preferred addend and gave a 63% yield of the 2,5-adduct as a mixture of exo and endo isomers. U.v. irradiation in acetone of the diester (16) derived from the endo adduct of phenol and N-phenylmaleimide gave the tricyclo[3.3.0.02,8]octan-3-one (17) in quantitative yield.

Mechanism of photochemical meta-cycloaddition of alkenes to the benzene ring: a novel type of molecular interaction

The regioselectivity of photochemical meta-cycloaddition of alkenes to alkylbenzenes changes progressively from 2,6- to 3,5- with increasing size of the alkyl group(s) while retaining endostereospecificity: this finding implies a novel type of weak but orienting intermolecular bonding interaction (intermolecular hyperconjugation) between S1 benzene and α-hydrogens on the alkene which can predominate over steric effects of bulky alkyl groups.

Thermal 2,5-cycloaddition of N-arylmaleimides to phenols

Phenol undergoes thermal 2,5-cycloaddition of N-phenylmaleimide to give endo- and exo-bicyclo-octenones (3) and (4) respectively, and a homopolymer of the maleimide; use of N-(p-methoxyphenyl)maleimide minimizes polymer formation, and gives a combined cycloadduct yield of 60% in the case of p-cresol.