Pulsed laser terpolymerization of styrene,methyl methacrylate and methyl acrylate

The propagation rate coefficient of the terpolymerization of styrene, methyl methacrylate and methyl acrylate in bulk was successfully determined at three different monomer compositions. The temperature was varied between 18 and 80°C. The resulting data at 50°C were not in agreement with predictions according to the terminal model with binary reactivity ratios that have been determined by fitting copolymer composition data with the terminal model. This indicates that here also the penultimate unit affects the kinetics.     

Atmospheric photodissociation lifetimes for nitromethane,methyl nitrite,and methyl nitrate

Atmospheric photodissociation rate coefficients and photodissociation lifetimes for nitromethane, methyl nitrite, and methyl nitrate were calculated as a function of altitude from their measured visible and near ultraviolet photoabsorption cross sections at 298 K. The lifetime of methyl nitrite is nearly independent of altitude and is approximately 2 min. From 0 to 50 km the lifetime of nitromethane varies from 10 to 0.5 hr, while that of methyl nitrate changes from 5.3 to 0.09 days, respectively.     

Studies on pyrrolidones. Convenient syntheses of methyl,methyl N-methyl- and methyl N-methoxymethylpyroglutamate

Facile methods to prepare methyl pyroglutamate ( 2 ), methyl N-methylpyroglutamate ( 1 ) and methyl N-methoxymethylpyroglutamate ( 7 ) in one-step from pyroglutamic acid are described.     

Michael additions to acrylonitrile,methyl acrylate and methyl vinyl ketone to Nb-benzylidenetryptophan methyl ester

Michael addition to methyl acrylate and methyl vinyl ketone of N_b-benzylidene-L-tryptophan methyl ester 1 gave 2-(3-indolylmethyl)glutamic dimethyl ester 2a and α-(3-oxobutyl)tryptophan methyl ester 2b respectively. Addition to acrylonitrile of 1 yielded α,N_a-dicyanoethyltryptophan methyl ester 3 .     

Radical terpolymerization of sulfur dioxide,hexene-1, and methyl acrylate or methyl methacrylate

The radical terpolymerization of sulfur dioxide, hexene-1, and methyl acrylate has been investigated, and from the dilution effects on composition of the terpolymer it would seem reasonable to rule out the possibility of the participation of the charge-transfer complex in the propagation process. We have also carried out terpolymerization of sulfur dioxide, hexene-1, and methyl methacrylate and obtained a terpolymer having the block nature.     

Copolymerizations involving methyl methacrylate,methyl acrylate,stilbene and p.fluorostilbene

Homopolymerizations and copolymerizations of methyl methacrylate (MMA) and methyl acrylate (MA) have been performed in the presence of either stilbene or p.fluorostilbene, labelled with carbon-14. It has been shown that at 60°C the polyMA radical is much more reactive than the polyMMA radical towards stilbene, the velocity constants for the reactions differing by a factor of about 300; similar results are found for p.fluorostilbene. The differences between the reactivities of the radicals are associated with steric effects arising from the presence of a methyl group at the alpha position in MMA.     

A comparative ab initio study of methyl formate, methyl thiolformate and methyl thionoformate

Ab initio SCF-MO calculations have been carried out for HCOOCH₃, HC(=O)SCH₃ and HC(=S)OCH₃. Relative stabilities of s-trans/s-cis conformers are reported and discussed in terms of specific intramolecular interactions. The energy difference between the s-trans and the s-cis form increases in the order methyl thiolformate < methyl thionoformate < methyl formate. The major stabilizing factors of the s-cis forms are the bond dipolar interaction and the mesomeric delocalization through the five member ring involving both the X=C---Y---C (X, Y = O, S) skeleton and the out-of-plane hydrogen atoms. These effects are used to explain the trends mentioned. The non-planarity previously proposed for the thionoester is reinvestigated. Our calculations show that this molecule is planar. Molecular atomic charges, dipole moments and ionisation potentials are determined and compared with available experimental values.     

Synthesis of methyl ethers of methyl (methyl β-D-galactopyranosid)uronate

The oxidation of methyl -D-galactopyranoside with oxygen in the presence of platinum and carbon gave methyl (methyl -D-galactopyranosid)uronate (I) with a yield of 20%. The partial methylation of (I) with methyl iodide in the presence of silver oxide followed by preparative liquid chromatography on silica gel provided a convenient method for obtaining all the methyl ethers in the individual state.Pacific Ocean Institute of Bioorganic Chemistry. Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 37–39, January–February, 1987.     

Syntheses of methyl α-dl-mycaminoside, methyl α-dl-oleandroside, methyl β-dl-cymaroside, methyl α-dl-tyveloside and methyl α-dl-chromoside C

Five rare hexoses, which are components of antibiotics or cardiac glycosides, have been synthesized as methyl glycosides through a common intermediate methyl 2,3-dehydro-2,3,6-trideoxy-α-dl glucopyranoside (7). Epoxidation and subsequent treatment with dimethylamine of7 afforded methyl α-dl-mycaminoside (9). The addition reaction of MeOH to12 gave methyl α-dl-oleandroside (15) and methyl β-dl-cymaroside (17). The hydroxymercuration and subsequent reduction of12 afforded methyl α-dl-chromoside C (19) and methyl β-dl-tyveloside (25).     

Crystallization curve of hexadecane in mixtures with methyl nonadecanoate,methyl octadecanoate,ethyl octadecanoate,and methyl hexadecanoate. A comparison of the experimental and calculated curves

The liquid—solid equilibrium temperatures in the binary systems between hexadecane and methyl nonadecanoate, methyl octadecanoate, ethyl octadecanoate, and methyl hexadecanoate are determined in order to obtain the interchange parameters between CH₃ or CH₂ and COO groups by means of group interaction statistics.     

Thiocyanation of N-aryl,N-acetyl,and N-[arylsulfonylimino(methyl)methyl] derivatives of 1,4-benzoquinone monoimine

N-[arylsulfonylimino(methyl)methyl] derivatives of 1,4-benzoquinone monoimine with alkyl substituents in the quinoid ring have been synthesized and their spectral characteristics were determined. The thiocyanation of N-aryl, N-acetyl, and N-[arylsulfonylimino(methyl)methyl] derivatives of 1,4-benzoquinone monoimine depending on the LUMO energy of the initial quinone monoamine affords derivatives of benzo[d][1,3]oxathiol-2-ones and benzo[d]oxazole-2(3H)-thiones.     

Reversible addition-fragmentation chain transfer copolymerization of methyl methacrylate and methyl acrylate

Pseudo-living radical copolymerization of methyl methacrylate and methyl acrylate under reversible addition-fragmentation chain transfer in a mass in the presence of reversible chain transfer agents of different nature was implemented. A comparison of physical and mechanical properties of narrowly dispersed copolymers was performed as well as copolymers obtained by uncontrolled radical polymerization.     

Photoinitiated polymerization of methyl methacrylate and methyl acrylate with 14C-labeled benzoin methyl ethers

Three ¹⁴C-labeled benzoin methyl ether (α-methoxy-α-phenylacetophenone) derivatives were utilized as photoinitiators in the polymerization of methyl methacrylate (MMA) and methyl acrylate (MA). The results of polymer end-group analysis are in accord with a mechanism of benzoin ether photocleavage into initiator radicals and dispute earlier labeling studies which were interpreted as evidence for copolymerization of excited-state benzoin ethers with reactive monomers. In MMA polymerization, the results indicate a preference for termination by disproportionation (～60%) and provide evidence for primary radical termination at 0.041M photoinitiator (optically dense solutions) in neat MMA. Evidence for chain branching by initiator radical hydrogen abstraction from poly(methyl acrylate) (PMA) is also presented. The benzoyl and α-methoxybenzyl radicals, produced on photolysis of benzoin methyl ether, appear to be equally effective in both initiation and hydrogen-abstraction processes. Quantum yields at 366 and 313 nm indicate the absence of a wavelength effect.     

The ground-state geometry of methyl fluoride

We have calculated the ground-state geometry for methyl fluoride from microwave spectroscopic rotational constants of five different isotopic species. The use of an A₀ value for CH₂DF was especially important in enabling us to define the CH distance within fairly narrow limits. The value so obtained is in good agreement with that predicted on the basis of the CH stretching frequency in CHD₂F, and it is also consistent with the trend of CH distances in other methyl halides.     

Proton affinities of saturated aliphatic methyl esters

The kinetic method was used to determine the proton affinities of methyl esters of several saturated fatty acids. Decompositions of the proton-bound dimers of the methyl esters, AHB⁺, were observed under different conditions with two instruments. The proton affinities (PAs) of the methyl esters increase continually with increasing carbon number in the acid. Equilibrium and initial rate experiments were performed with a Fourier transform ion cyclotron resonance mass spectrometer on the methyl ester of the C₂₂ saturated acid (methyl behenate). These experiments give values for PA (methyl behenate) that are perhaps slightly lower than those obtained with the kinetic method. The PAs of the methyl esters of the fatty acids could be correlated with the equation: PA (ester) = (40.0 ± 2.5)*log(n) + (784.7 ± 3.9) kJ/mol or PA (ester) = (864 ± 2) − (479 ± 41)/n, wheren = number of atoms in the molecule. Proton affinities of smaller sets of 1-alkylamines and 1-alkanols can be fit to similar equations.     

Asymmetric syntheses of methyl N-Boc-2-deoxy-2-amino-l-erythroside,methyl N-Boc-2-deoxy-2-amino-d-threoside and methyl N-Boc-2,3-dideoxy-3-amino-l-arabinopyranoside

The asymmetric syntheses of methyl N-Boc-2-deoxy-2-amino-l-erythroside and methyl N-Boc-2-deoxy-2-amino-d-threoside have been achieved from sorbic acid, in six and eight steps, and in 35 and 13% overall yield, respectively. Diastereoselective aminohydroxylation of tert-butyl sorbate gives access to two diastereoisomeric α-hydroxy-β-amino-γ,δ-unsaturated esters. Reduction of the ester functionality and ozonolysis of the double bond gives the corresponding aldehyde, which exists exclusively in the ring-closed (furanose) form. An alternative synthesis of methyl N-Boc-2-deoxy-2-amino-l-erythroside was also developed, reliant on aminohydroxylation of an α,β-unsaturated ester bearing an acetal functionality at the γ-position, and this synthesis proceeded in five steps and 54% overall yield from acrolein diethyl acetal. This approach was extended to permit the synthesis of methyl N-Boc-2,3-dideoxy-3-amino-l-arabinopyranoside in six steps and 58% overall yield from ethyl 3,3-diethoxypropanote.     

Photo-copolymerization of methacryloyl-L-valine methyl ester,methacryloyl-D-valine methyl ester,and maleic anhydride

Photocopolymerization of methacryloyl-L -valine methyl ester (L-MAVM), methacryloyl-D -valine methyl ester (D-MAVM) and maleic anhydride (MAn) was carried out in dioxane at 25°C without initiator at an initial total concentration of the three monomers of 1 mole/1.; the molar ratio of MAn in the feed to the sum of L- and D-MAVM was 1 : 1 in all cases. The copolymer with a 1 : 1 molar ratio of MAVM and MAn was always obtained regardless of the feed molar ratio of L- and D-MAVM. The circular dichroism (CD) spectra of the copolymer before and after hydrolysis showed a linear relationship between the monomer unit ellipticity at 222 nm and the molar feed ratio of L- and D-MAVM and suggested the induction of an asymmetric center into the polymer main chain. The results also indicated that the configuration of the induced asymmetric carbon atoms would be arranged according to that of fed MAVM monomer.     

Structure and characteristics of film composites based on methyl cellulose,poviargol, and montmorillonite

The structure of film composites based on methyl cellulose and fillers, such as montmorillonite and silver nanoparticles stabilized by poly(vinylpyrrolidone) (Poviargol), is studied by X-ray diffraction. In the composite, montmorillonite nanoparticles exist in the exfoliated state; when the content of the nanoparticles is below 7 wt %, the crystallinity of methyl cellulose increases. Owing to the presence of the filler and structural ordering of the matrix, elastic characteristics improve and the degradation temperature of the composites increases. The X-ray structural data show that the Ag particles in the methyl cellulose-Poviargol composite are 30 nm in size. The introduction of up to 20 wt % Poviargol assists the crystallization of methyl cellulose. The strength and strain characteristics of the film composites based on methyl cellulose and Poviargol make it possible to use these composites in medicine and agriculture.     

Model studies for the thiol-mediated methyl transfer to corrinoids

The thiol-dependent methylation of heptamethyl cob(II)yrinate 8r with methyl iodide and methyl tosylate was explored under a variety of conditions. The interaction of the heptamethyl cob(II)yrinate with a variety of thiols was monitored prior to the addition of the methylating agent, and the formation of the Co(I) complex was only apparent in the reaction with hexane thiol. Nevertheless, thiol-mediated methylation of the Co(II) complex 8r takes place with methyl iodide under most conditions. The Co-methylation with methyl tosylate showed a different reactivity, was inhibited by pyridine or N-methylimidazole, and was strongly dependent on the the acidity of the thiol used. Mechanistic aspects are discussed.