Topic
Substituent
About: Substituent is a research topic. Over the lifetime, 42877 publications have been published within this topic receiving 516716 citations. The topic is also known as: side chain & side group.
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Patent•
06 Dec 1999TL;DR: In this paper, an organic EL device, including an anode and a cathode, and at least one organic luminescent layer containing a compound of the formula: STR 1, where X =S, or O R 1, and R 2 are individually alkyl of from 1 to 20 carbon atoms.
Abstract: An organic EL device, including an anode and a cathode, and at least one organic luminescent layer containing a compound of the formula: ##STR1## wherein: X=S, or O R 1 , and R 2 are individually alkyl of from 1 to 20 carbon atoms, aryl or carbocyclic systems; R 3 , and R 4 are individually alkyl of from 1 to 10 carbon atoms, or a branched or unbranched 5 or 6 member substituent ring connecting with R 1 , R 2 respectively; and R 5 and R 6 are individually alkyl of from 1 to 20 carbon atoms, which are branched or unbranched.
164 citations
TL;DR: Mass spectrometric analysis using positive- and negative-ionization modes was carried out on derivatized compound C, suggesting that the biologically active compound C was 12(R)-hydroxy-5,8,10,14-icosatetraenoic acid, which may have an important role in regulating ocular transparency and aqueous human secretion.
Abstract: When corneal microsomes were incubated with arachidonic acid in the presence of an NADPH-generating system, four polar metabolites (compounds A-D) were formed. Synthesis of these metabolites could be inhibited by carbon monoxide, SKF 525A, and anti-cytochrome c reductase antibodies. One of the metabolites, compound C, was found to inhibit partially purified Na+,K+-ATPase from the corneal epithelium in a dose-dependent manner with an ID50 of approximately 50 nM. After compound C was purified by TLC and HPLC, it was found to have a UV absorption spectrum with a maximum absorbance at 236 nm suggesting the presence of a conjugated diene. Mass spectrometric analysis using positive- and negative-ionization modes was carried out on derivatized compound C that had been synthesized from a mixture of specifically labeled ([5,6,8,9,11,12,14,15-2H8]arachidonic acid) and unlabeled arachidonic acid. Abundant fragment ions were consistent with compound C being a monooxygenated derivative of arachidonic acid with a hydroxyl substituent at carbon-12 of the icosanoid backbone; all deuterium atoms from [2H8]arachidonate were retained in the structure. Oxidative ozonolysis yielded products indicating double bonds between carbons at positions 10 and 11 and positions 14 and 15 of the 20-carbon chain. Compound C was, therefore, characterized as a 12-hydroxyicosatetraenoic acid. However, only 12(R) isomer was found to be an inhibitor of the Na+,K+-ATPase from the corneal epithelium, suggesting that the biologically active compound C was 12(R)-hydroxy-5,8,10,14-icosatetraenoic acid. Such an inhibitor of Na+,K+-ATPase synthesized in the cornea may have an important role in regulating ocular transparency and aqueous human secretion.
164 citations
TL;DR: In this article, aryl−aryl sandwich complexes were studied experimentally and theoretically and the experimental π-stacking free energies were shown to correlate well with Hammett σm constants (r = 0.96).
Abstract: Stereoselective Diels−Alder cycloadditions that probe substituent effects in aryl−aryl sandwich complexes were studied experimentally and theoretically. Computations on model systems demonstrate that the stereoselectivity in these reactions is mediated by differential π-stacking interactions in competing transition states. This allows relative stacking free energies of substituted and unsubstituted sandwich complexes to be derived from measured product distributions. In contrast to gas-phase computations, dispersion effects do not appear to play a significant role in the substituent effects, in accord with previous experiments. The experimental π-stacking free energies are shown to correlate well with Hammett σm constants (r = 0.96). These substituent constants primarily provide a measure of the inductive electron-donating and -withdrawing character of the substituents, not donation into or out of the benzene π-system. The present experimental results are most readily explained using a recently proposed m...
163 citations
Patent•
15 Jan 2002
TL;DR: In this paper, a negative image-recording material for heat-mode exposure systems, which comprises an IR absorbent including cyanine dye having a substituent that contains an atom having an atomic weight of at least 28 such as halogen atom, or a non-covalent electron pair such as carbonyl group, and a radical generator and a radically polymerable compound, was presented.
Abstract: The invention provides a negative image-recording material for heat-mode exposure systems, which comprises (A) an IR absorbent including cyanine dye having a substituent that contains an atom having an atomic weight of at least 28 such as halogen atom, or a substituent that contains a non-covalent electron pair such as carbonyl group, (B) a radical generator and (C) a radically-polymerable compound, and which is imagewise exposed to IR rays for image formation thereon.
162 citations
TL;DR: In this paper, the steric purity of polymers with an ordered steric structure has been investigated and the relationship between steric structures and crystallinity has been discussed. But it has been shown that a regular steric shape is a necessary, but not a sufficient condition for the crystallizability of the polymers, and it is possible to obtain polymers from isotactic, amorphous, not crystallizable polymers.
Abstract: Results of new research work in the field of polymers with an ordered steric structure, obtained by stereospecific polymerization, are reported Some of the results concern the relationship between steric structure and crystallinity; from these it results that a regular steric structure is a necessary, but not a sufficient condition for the crystallizability of the polymers
In the isotactic polymers of CH2=CHR type monomers, the shape and size of the R group not only determine the different conformation of isotactic helices (with a number of monomeric units per pitch varying form 3 to 4) but in some particular cases are responsible for the lack of crystallinity
It is possible, through chemical processes which modify the shape and size of the R substituent, to obtain crystalline polymers from isotactic, amorphous, not crystallizable polymers
The crystalline structure of syndiotactic polypropylene is described for the first time and is compared with the structure of other syndiotactic polymers
Furthermore the structure of crystalline polymers of “di-isotactic type”, obtained polymerizing RCH=CHR1 type monomers is discussed; and a nomenclature for the different possible stereoisomers is suggested
Cases of polymorphism, isomorphism and di-isomorphism in the macromolecular field are examined and a new type of isomorphism among different monomeric units is discussd Crystalline copolymers of isomorphous monomeric unit is discussed Crystalline copolymers of isomorphous monomeric units have a melting point which is intermediate between the ones of the corresponding pure homopolymers
The effects which influence the steric purity of polymers having an ordered structure are discussd and the influence of steric purity of the physical properties and mainly on the mechanical properties of the polymers (especially for the case of polybutadiene obtained at the Polytechnic of Milan with a percentage of cis 1,4 units higher than 99%) is pointed out
162 citations