Cornelis Jacobus Groenenboom

β-substituted alkyltin halides : II. Dialkyltin dihalides: mechanistic and spectroscopic aspects☆

Abstract Hydrogen halides, tin and α,β-unsaturated carbonyl compounds react together under mild conditions to give mixtures of β-substituted alkyltin trihalides and bis(β-substituted alkyl)tin dihalides: acrylonitrile is also active. Spectroscopic data for a number of pure functionally substituted dialkyltin compounds is presented. The monoalkyltin compounds are almost certainly formed by the in-situ formation of trihalogenostannanes from hydrogen halides and tin. Several possible mechanisms are discussed for the formation of the dialkyltin compounds. The substituted monoalkyltin compounds react with tin to give the corresponding dialkyltin compounds as well as products which are believed to be relatively stable tin—tin species.

Photoinitiators and photoinitiation Part 11. The photodecomposition of some O-acyl 2-oximinoketones

The photodecomposition of several O-acyl 2-oximinoketones was studied using electron spin resonance and proton nuclear magnetic resonance chemically induced dynamic nuclear polarization techniques. Primary NO bond cleavage into α-ketoiminyl and acyloxy radicals from the triplet excited state was observed in all cases. α-Ketoiminyl radicals observable at T < −70°C underwent rapid fragmentation into a benzoyl radical and a nitrile at temperatures exceeding −60°C. Chemical evidence was provided by radical trapping using a thiol and a stable nitroxyl respectively. These experiments also showed that, for most O-acyl 2-oximinoketones 1, [E] ⇌ [Z] photisomerization was the major process, whereas for O-acyl 2-oximinoketones 2 photodecomposition was almost exclusive.

Photoinitiators and photoinitiation 10. The photodecomposition of some carboxylic esters of α-hydroxymethylbenzoin

Abstract The photodecomposition of some carboxylic esters of α-hydroxymethylbenzoin was studied using electron spin resonance (ESR) and proton nuclear magnetic resonance-chemically induced dynamic nuclear polarization ( 1 H NMR-CIDNP) techniques. Exclusive α-cleavage into benzoyl and α-hydroxy-α-acyloxymethylbenzyl radicals through the triplet excited state was observed. The α-hydroxy-α-acyloxymethylbenzyl radicals mainly undergo disproportionation with the other radicals present to give benzoylmethyl carboxylates. Elimination of carboxylic acids from the α,α-disubstituted benzyl radicals occurs to some extent, but at a much lower rate than the elimination of sulphonic acids from the corresponding α-hydroxy-α-sulphonyloxymethylbenzyl radicals generated from the sulphonic esters of α-hydroxymethylbenzoin.

β-Substituted alkyltin halides: III. Synthesis of trialkyltin halides and tetraalkyltins☆

Abstract (β-Carboalkoxyethyl)tin trihalides and bis(β-carboalkoxyethyl)tin dihalides react with metallic zinc to give mixtures of the corresponding tris(β-carboalkoxyethyl)tin halides and the tetra(β-carboalkoxyethyl)tins. Bis(β-carboalkoxyethyl)tin diacetates react with metallic zinc to give only the corresponding tetra(β-carboalkoxyethyl)tin compounds. The mechanisms of these reactions are discussed. Conversion of the bis(β-carboalkoxyethyl)tin dihalides into the tris(β-carboalkoxyethyl)tin halides is believed to occur by a two-step process, with the tetra(β-carboalkoxyethyl)tin compounds as intermediate products. The 270 MHz NMR spectra of the (β-carbobutoxyethyl)tin compounds are presented.