Matrix polycondensation through hydrogen bonding interaction

Polycondensation of diesters having hydroxyl or pyridine groups was carried out with hexamethylenediamine (HMD) in the presence of (vinyl alcohol/vinyl acetate) copolymers as a matrix polymer. Apparent rates of the polycondensation of dimethyl tartrate (DMT) with HMD increased with increasing contents of PVA units in the copolymers and a strong entanglement between growing polyamide chains and PVA copolymers took place through the adsorption of HMD and DMT on the matrix copolymers. 2,6-Dimethyl pyridine dicarboxylate (2,6-DMP) reacted with HMD in the presence of the PVA copolymers or polysaccharide, while the rate enhancement effect of the matrix polymers was not significantly observed, as in the case of DMT. The effect of the matrix polymers on the polycondensation was discussed in terms of hydrogen bonding interactions.     

Formation of n-alkyl-n(1-hydroperoxyalkyl)nitrosamines from n-alkyl-n-(1-acetoxyalkyl)nitrosamines

N-alkyl-N-(1-hydroperoxyalkyl)nitrosamines were prepared by treatment of the corresponding 1-acetoxyalkyl nitrosamines with hydrogen peroxide in acetic acid through an acid-catalyzed nucleophilic substitution.     

Grafting onto carbon black by the reaction of reactive carbon black having epoxide groups with several polymers

The grafting of functional polymers onto carbon black surface by the reaction of epoxide groups introduced onto the surface was investigated. The introduction of epoxide groups was achieved by the reaction of the phenolic hydroxyl and carboxyl groups on carbon black with chloromethyloxirane in the presence of sodium hydroxide. The amount of epoxide groups introduced onto the channel black Neospectra II was equal to 0.40 meq/g. The epoxide groups were reacted with polypropylene glycol, silicone diol (SDO), silicone diamine (SDA), and polyethyleneimine to give polymer-grafted carbon blacks. For example, the percentage of grafting of SDO (M_n = 1.0 × 10³) and SDA (M_n = 3.9 × 10³) reached to 23.6 and 67.2%, respectively. The percentage of grafting increased with the molecular weight (M_n) of the polymers, while the number of grafted chain (G_n) decreased. In the case of SDO, the relationship between M_n and G_n was found to be G_n = 4.68 × 10^?2 M. The carbon black obtained from the reaction gave stable colloidal dispersions in tetrahydrofuran and the stability of dispersion increased with an increase in the percentage of grafting.     

A direct method for the separation and quantification of bile acid acyl glycosides by high-performance liquid chromatography with an evaporative light scattering detector

A direct method for the separation and quantification of a series of bile acid acyl glycosides using high-performance liquid chromatography coupled to an evaporative light scattering detector (HPLC-ELSD) is described. Complete separation of each of 15 bile acid acyl 24-alpha-glucosides and their 24-beta-anomers and 24-beta-galactosides was achieved by the stepwise gradient elution mode on a C18 column using a mixture of acetonitrile-methanol (8:2, v/v) and 1% aqueous acetic acid as the mobile phase. 24-beta-Galactosides were always eluted faster than the corresponding 24-beta-glucosides, which eluted after the corresponding 24-alpha-anomers. Calibration curves of different 24-beta-galactosides were linear over a range of 0.2-40 nmol of injected amount and the detection limits (S/N > 3) were from 0.08 to 0.1 nmol. The present HPLC-ELSD method may provide an insight into the separation and quantification of the biologically interesting neutral bile acids.     

Photocontrol of micellar catalysis

A photoresponsive surfactant with a cationic azobenzene head group (I) was synthesized. It was demonstrated that by mixing (I) with a conventional cationic micelle the rate of the micelle-catalyzed reaction (base-catalyzed proton abstraction from benzoin) can be controlled by light. The origin of the photocontrol was accounted for by the difference in the partitioning of trans-(I) and cis-(I) in the micelle phase.     

Endgroup study of chlorate–sulfite-initiated acrylonitrile copolymer

Quantitative determination of endgroups in an acrylonitrile–methyl acrylate (90:10) copolymer polymerized with NaClO₃–Na₂SO₃ redox system in aqueous solution was carried out by conductometric and dyeing methods for SO₃H incorporated into polymer, x-ray analysis for S in polymer, and polarography for Cl in polymer. The number-average molecular weight was measured by osmometry. Determination of endgroups was done on both unfractionated polymer and fractionated polymer. On the average, 0.95 mole S and 0.71 mole SO₃H per molecule were found in unfractionated polymer. For fractionated polymer, 0.68 mole S and 0.69 mole SO₃H per molecule were found. A small amount of Cl was also found in both unfractionated polymer and fractionated polymer. The difference between results for the two polymers and polymerization kinetics are discussed.     

Novel copper hydride-promoted 1,3-rearrangement of α-allenylcyclopropane systems to methylenecyclopentenes

α-Allenylcyclopropanedicarboxylates, for which a novel synthetic method has been devised by conjugate addition of a copper hydride (Stryker) reagent to α-cyclopropylpropargylic esters, have been newly found to be smoothly converted to methylenecyclopentene derivatives under mild reaction conditions by further treatment with the copper hydride reagent. The mechanistic pathway is discussed.     

Sound attenuation by multiple barriers

A method (tentatively called ‘the method of equivalent sound source’) of predicting the sound attenuation achieved by multiple barriers with knife edges and/or right-angled wedges is proposed. This paper shows that the sound pressure level in the shadow region behind the multiple barriers can be obtained by successively setting imaginary sound sources for respective edges and/or wedges. The locations of the imaginary sound sources are determined by means of the traditional solution for sound attenuation by a single edge. The calculated results for several kinds of small-scale model, obtained by ‘the method of equivalent sound source’, are compared with experimental results.