• Journal of the Korean Ceramic Society
• /
• v.24 no.6
• /
• pp.561-571
• /
• 1987

In case of glass ceramics and powder preparation from the metalakoxide solutions, metalakoxide solutions with a various species of alkoxy groups have unique characteristics. Therefore, in this study, the mixing ability of homogeneous sol, gel morphology and physical properties of gels were investigated by the changes in terms of the different four alkoxy groups, CH3-, C2H5-, i-C3H7-n-C4H9-, along with the catalyst for the purpose of the observation about the homogenous transition range from sol to gel. As a result, when the fixed condition was mol ratio of H2O/Si(OR)4=2.0 and variables were batch composition and addition amount of catalyst, the characteristics of Tetra-normal-Butoxysilane and Tetra-iso-propoxysilane systems had very narrow sol-gel conversion region than Tetramethoxysilane and Tetraethoxysilane system. And silicon-alkoxide, systems having narrow sol-gel conversion region were enlarged by addition of catalyst. In viewpoint of the weight loss of gel produced by hydrolysis of silicon alkoxide systems with different four alkoxy groups, the amounts of weight loss of gel containing large molecular alkoxy groups were much more than those of small molecular alkoxy group.

• Journal of Microbiology and Biotechnology
• /
• v.13 no.4
• /
• pp.632-635
• /
• 2003

Novel poly(3-hydroxyalkanoates), PHAs, having either methoxy or ethoxy groups as the terminal hydrophilic moieties, were biosynthesized by Pseudolnons oleovorans. grown either solely with 11-alkoxyundecanoic acid or 8-alkoxyoctanoic acid, or grown with a mixture of 6-alkoxyhexanoic acid and nonanoic acid. The PHA synthesized from 11-methoxyundecanoic acid consisted of 88 mol% 3-hydroxy-7-methoxyheptanoate and 12 mol% 3-hydroxy-9-methoxynonanoate. However, the PHA produced from 11-ethoxyundecanoic acid consisted of 56 mol% 3-hydroxy-5-ethoxypentanoate and 44 mol% 3-hydroxy-7-ethoxyheptanoate. The high solubility of the PHAs in methanol and ethanol indicated that the alkoxy groups in the side chains resulted in the formation of PHAs with an enhanced hydrophilicity.

• Journal of the Korean Society of Industry Convergence
• /
• v.12 no.3
• /
• pp.143-147
• /
• 2009

The enantioselective reduction of representative prochiral alkyl-aryl ketones with a new chiral alkoxy-amine-aluminum derivatives from aluminum hydride and ${\alpha},{\alpha}$-diphenyl-${\beta}$-amino alcohols, such as (S)-(-)-2-amino-3-methyl-1,1-diphenylbutan-1-ol(AMDPB) and (S)-(-)-2-(diphenylhydroxy-methyl)pyrrolidine(DPHMP), in THF at $0^{\circ}C$ was studied. In the reduction of alkoxy-amine-aluminum derivatives, acetophenone, propiophenone, isopropiophenone, and butyrophenone are reduced to corresponding aromatic secoundary alcohols with 34~60 % enantiomeric excess of (S)-isomers. For such ketones, the optical induction was enhanced by increasing a size of alkyl groups.

• Bulletin of the Korean Chemical Society
• /
• v.20 no.1
• /
• pp.42-48
• /
• 1999

We have performed a quantum-chemical investigation on the conformations and electronic properties of a variety of methoxy-substituted poly(p-phenylenevinylenes) (PPVs) to elucidate the effects of alkoxy substitution. Geometrical parameters for the polymers were fully optimized through Austin Model I (AM I) semi-empirical Hartree-Fock (HF) band calculations. Electronic properties of the polymers were obtained by applying the AM I optimized structures to the modified extended Huckel method. To confirm validity of the AM I conformational results, we also carried out ab initio HF calculations with the 6-31G (d) basis set for a variety of methoxy-substituted divinylbenzenes. It is found that the potential energy surfaces of alkoxy-substituted PPVs are quite shallow around the planar conformations, suggesting that the prepared films possess a variety of conformations with different torsion angle in the solid state, depending on the synthetic conditions. When two alkoxy groups are concurrently substituted at the adjacent sites in the phenylene ring, these groups are subject to rotating around the C(sp2)-O bonds by 70-80° to avoid the strong steric repulsion between them. Consequently, the overlap between the π-type p orbital of oxygen and the π molecular orbitals of the polymer decreases. This leads to a wide gap and a high oxidation potential for tetramethoxy-substituted PPV, compared to those of dialkoxy-substituted PPV.

• Bulletin of the Korean Chemical Society
• /
• v.19 no.2
• /
• pp.243-249
• /
• 1998

The reaction of alcohol with a solution of thexylborane (ThxBH2) in tetrahydrofuran (THF) provides a new class of mild and selective reducing agents, thexylalkoxyboranes (ThxBHOR: R=Et, i-Pr, i-Bu, s-Bu, t-Bu, Ph). In order to elucidate the effect of the alkoxy group in reduction reactions, the reducing power of ThxBHOR toward selected organic compounds containing representative functional groups under practical conditions (THF, 25°, the quantitative amount of reagent to compound) has been investigated. Generally, the reactivity of ThxBHOR is largely dependent upon the alkoxy substituent. ThxBHOR can be synthesized from a variety of alcohols, thus allowing control of the steric and electronic environment of these reagents.

• Bulletin of the Korean Chemical Society
• /
• v.20 no.8
• /
• pp.929-934
• /
• 1999

2-( β-Alkoxyvinyl)-4-(1-hydroxyalkyl)pyrroles (14) were synthesized from 4-acylpyrrole-2-carboxylates (8) by sequential reduction of their acyl and alkoxycarbonyl groups to give 4-(1-hydroxyalkyl)pyrrole-2-carbalde-hydes (13) followed by Wittig reaction of the aldehydes with the ylide of alkoxymethylphosphonium chloride. Diels-Alder reaction of 2-(β-alkoxyvinyl)-4-(1-hydroxyalkyl)pyrroles with trans-methyl β-nitroacrylate gave 6-alkoxy-3-(1-hydroxyalkyl)-5-nitro-4,5,6,7-tetrahydroindole-4-carboxylates (3).

• Bulletin of the Korean Chemical Society
• /
• v.8 no.4
• /
• pp.276-280
• /
• 1987

Several chiral potassium B-alkyl-9-boratabicyclo[3.3.1]nonanes $(K\; B-R^*-9-BBNH)$ and potassium B-alkoxy-9-boratabicyclo[3.3.1]nonanes $(K \;B-OR^*-9-BBNH)$ were synthesized by treatment of the corresponding trialkylboranes and dialkylmonoalkoxyboranes with a small excess of potassium hydride. The chiral B-alkoxy derivatives generally reduce representative ketones, such as acetophenone and 3-methyl-2-butanone, with greater optical induction than the corresponding B-alkyl derivatives, suggesting the involvement of the oxygen atom in the control process for asymmetric synthesis.

• The Korean Journal of Pesticide Science
• /
• v.6 no.2
• /
• pp.58-63
• /
• 2002

New photodynamic herbicidal 2,3-dihydro-2,2,4,5,6-pentamethylbenzofuran-5-yl, (I) and 2,3-dihydro-2-ethyl-2,4,5,6-tetramethylbenzofuran-5-yl, (II) substituents in 6-benzofury-2-[1-( alkoxyimino )alkyl]-3 hydroxycyclohex-2-en-1-one derivatives were synthesized and their herbicidal activities against rice plant (Oryza sativa L.), barnyard grass (Echinochloa crus-galli) and pickerel weed (Monochoria vaginalis presl.) were measured under submerged pre and post-emergence conditions. Particularly, a series of (I) compounds showed good selective herbicidal activities between the 3 leaf stage of rice plant and barnyard grass at rates of $0.25{\sim}0.0007kg/ha$. The structure activity relationships (SAR) on the herbicidal activity with changing N-alkoxy groups were discussed quantitatively. According to the SAR results, it was expected that the selectivity factor between seed of rice plant and barnyard grass should be rely on the N-alkoxy groups with bigger dipole moment and bigger (or smaller) $B_3$ constant than optimal value $(B_3)_{opt.}=4.41{\AA}$. Compared with (I), the (II) substituents showed more superior herbicidal activities.

• The Korean Journal of Pesticide Science
• /
• v.4 no.2
• /
• pp.69-71
• /
• 2000

The herbicidal activities ($pI_{50}$) with alkoxy (RO-) groups on the azomethine nitrogen atom in 5-(2,3-dihydro-2,2-dimethylbenzothiophene-7-yl)-2-(1-(alkoxyimino)butyl)-3-hydroxy-2-cyclohexene-1-one derivatives against various weeds were measured in the flooded and in the paddy conditions. Particularly, i-propoxy subsutuent, 5 of them showed excellent herbicidal activity at a rate of 4kg/ha with pre-emergence against barnyard grass (Echinochloa crus-galli) with good selectivity on rice plant (Oryza sativa). The results of the structure-activity relationships (SAR) analyses are shown that the alkyl subsituents with higher hydrophobicity (logp>0) and electron donating (${\sigma}^*<0$) group as a new substrate rather than alkoxy substituents seems to be contribute to the herbicidal activity with pre-emergence.

• Journal of the Korean Ceramic Society
• /
• v.28 no.12
• /
• pp.975-980
• /
• 1991

Chelated titanium alkoxides are hydrolysed showly and stable enough to prepare multicomponent gels of titania without its precipitation due to the fast hydrolysis of Ti alkoxide. The alkoxy groups of chelated titanium alkoxide are hydrolysed as fast as that of titanium alkoxide but the chelating groups are stable even in aqueous solution. The chelating groups showed different rates of hydrolysis in aqueous ammonia solution and water added one. Those rates were monitored with UV-VIS spectrophotometer by using their unique absorption bands before and after hydrolysis.