substituent


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substituent

[səb′stich·ə·wənt]
(organic chemistry)
An atom or functional group substituted for another in a chemical structure.
References in periodicals archive ?
The XRD results described above demonstrated again that the alkyl substituent chains had a great effect on the assembly modes of these imide compounds.
Table 3: [DELTA]i value of -[CH.sub.2] increased by the substituent group (X or Y) in X-[CH.sub.2]-Y Substituent group [DELTA]i Substituent group [DELTA]i -[CH.sub.3] 0.47 -CO-OR 1.55 -COR 17 -OCO-R 3.13 -Br 2 33 -[C.sub.6][H.sub.5] 1.85 -OR 2.36 where 0.23 is the basic number of -[CH.sub.2] protons, and [DELTA]i is the protonational chemical shift increase of -[CH.sub.2] protons.
The carcinogenic activity of poly cyclic aromatic hydrocarbon (PAHs) highly varied with the presence of methyl substituent on the aromatic ring of the PAHs [14].
Log P, MV= molar volume, MR= molar Refractivity and [pi] = value for Particular Substituent No.
The methylenedioxy substituent is derived biosynthetically from the cyclization of a precursor such as 3-methoxy-4,5-dihydroxyphenethylamine or 3,4-dimethoxy-5-hydroxyphenethylamine.
Preliminary calculations [10, 11], made with the density functional theory (DFT) using the B3LYP exchange-correlation functional at the 3-21+[G.sup.*] and 6-31+[G.sup.*] levels and the PM3 semi-empirical method, showed that adding some electronegative substituents increases acidity, but also increases the tendency of the fragmentation of the boron cage.
In the past decade or so, however, chemists have made some stable carbenes by bonding the central carbon to two bulky substituents, or groups of atoms.
The ds.DNA binding capacity of these FC derivatives was studied at room temperature and an understanding of the substituent effect was developed.
The substituent effect on the O-H bond dissociation energy (BDE) of phenols has been shown to depend on factors such as inductive or electrostatic effect, resonance effect, and hydrogen-bonding interactions in the respective solvents [15].
Prop-2-en-1-ones are [alpha], [beta]-unsaturated ketones consist of two aromatic rings having diverse array of substituent. Aromatic rings are interconnected by a highly electrophilic three carbon a, [beta]-unsaturated carbonyl system, which assumes linear or nearly planar structure [1].
The presence of a methyl substituent at meta position in 5 gave better penetration into the bacterial cell wall via suitable binding [33].
PMMA, PTFEMA, PPhMA, and PPFPhMA showed four types of birefringence properties, even though they were all methacrylates and their molecular structures only differed in terms of the substituent R in the side chains, as shown in Fig.