Showing papers on "Intramolecular reaction published in 1973"

Friedel‐Crafts crosslinking of polystyrene

Abstract: Polystyrene may be crosslinked by p-dichloromethylbenzene (DCMB) in 1,2-dichloroethane solution with SnCl4 as catalyst. Combined intra- and intermolecular crosslinking can be measured by evolution of hydrogen chloride and by an ultraviolet spectral method, and the results for the two methods are in excellent agreement. Intermolecular crosslinking may be calculated separately from number-average molecular weight measurements, so that the extent of intramolecular crosslinking may be deduced by difference. Rate equations for the overall, intermolecular, and intramolecular reactions have been obtained as follows: The anomalous behavior with respect to polystyrene concentration may be due to inhibition of the intramolecular reaction because of increasing interpenetration of polystyrene molecules as the concentration of polystyrene is increased. The rate constant for the intermolecular reaction, which shows “normal” kinetic behavior has been compared with values for the reaction of DCMB with the model compounds benzene, toluene, diphenylmethane, and benzyl chloride. The very much smaller value for polystyrene compared with the models has been accounted for in terms of adverse steric effects when the reaction is occurring in the polymer chain environment.

The intramolecular reaction between a diazoalkane group and an ester group: a search for other examples

Abstract: The reactions of eight N-nitroso-lactams with sodium methoxide are described. In most cases the intermediate diazoalkane ester does not give an insertion product of the kind described in the preceding paper, but gives instead the solvolysis products—ethers and/or olefins. The intramolecular reaction between a diazoalkane and an ester group is not therefore a promising one for synthesis. One other example of the diazoalkane ester reaction was, however, observed: 4-nitroso-4-azahomoadamantan-5-one (24) gave a 14% yield of methyl noradamantane-3-carboxylate (27). One other nitroso-lactam, 3-nitroso-3-aza-A-homocholest-4a-en-4-one (32), failed even to give a diazoalkane, but instead rearranged to an isomer, methyl (3-nitroso-3-aza-A-nor-5ξ-cholestan-5-yl)acetate (34).The partitioning of the intermediate diazotic acids between diazoalkane and solvolysis products indicates that substantial yields of diazoalkanes were realised in most cases. The synthesis of the N-nitroso-lactams is described.

Kinetic Theory for Some Intramolecular Reactions Proceeding on a Polymer Chain. II.

Abstract: Kinetic theory for the reactions proceeding on a polymer chain was developed in the field of polymer catalyst. Polymer catalyst is designed to possess either adsorption or catalytic site distributed along the chain. The former adsorbs a substrate and the complex formed subsequently undergoes an intramolecular reaction catalyzed by the latter to afford product and to regenerate free adsorption site. The overall reaction rate was formulated taking into account the distribution of catalytic sites in the neighborhood of each adsorption site. The reaction rate for polymer catalyst was compared with that for the corresponding low-molecular-weight catalyst. The acceleration by polymer catalyst was very marked when the reagent concentrations were low. A supplementary remark on Part I of this series was also made.

The intramolecular reaction between a diazoalkane group and an ester group: the second example

Abstract: The isomeric nitroso-lactams, cis- and trans-9-hydroxy-4-nitroso-4-azahomoadamantan-5-ones (11) and (13), have been synthesised and treated with sodium methoxide. The major products were the unexceptionable solvolysis products, the methyl cis- and trans-9-hydroxybicyclo[3.3.1]non-7-ene-3-endo-carboxylates, which were actually isolated as their dihydro-derivatives (27) and (29). In the latter case, methyl 9-oxatricyclo[5.2.1.03,8]decane-5-endo-carboxylate (28) was also formed. The minor products, the methyl trans- and cis-9-hydroxynoradamantane-3-carboxylates (12) and (14), respectively, were the result of a diazoalkane ester insertion reaction. The configurations of the nitroso-lactams were determined directly from n.m.r. spectra, and the configurations of the products were determined from the trisdipivaloylmethanatoeuropium(III)-shifted n.m.r. spectra.The low yield of these products is evidently a consequence of the low yield of the diazoalkane. The diazoalkane ester insertion reaction, however, is so favoured that all the diazoalkane formed is converted into the noradamantane, even in the absence of a protic solvent.

Effect of intramolecular reaction on elution of methyl α,β- thioglycidates in gas chromatography

Abstract: The esters of methyl-substitutedα,β-thioglycsdic acids have the same inversion of the exit as the corresponding ester derivatives. The elution order is determined by the intramolecular reaction of the carbomethoxyl groups with the substituents. The obtained data can be used to confirm the structures of the studied compounds.

Some transformations of secondary and tertiary triorgano-β-aminoethylsilanes

Abstract: 1. A study was made of the characteristics of the reactions for the decomposition of the Si-C bonds in triorgano-β-aminoethylsilanes. The stability of the Si-C bond inβ-aminoethylsilanes is determined by the possibilities of intramolecular reaction between the silicon and nitrogen atoms. 2. It was shown thatβ-aminoethylsilanes, containing functional groups attached to the Si atom, can undergo substitution, reduction and condensation reactions without cleaving the Si-C bond.