Substituent Content

Moreover, an increase in hydrophobicity of the polymer has been observed with the presence of longer side chains [59]. 

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C. Alvarez-Lorenzo, R. A. Lorenzo-Ferreira, J. L. Gomez-Amoza, R. Martinez-Pacheco, C. Souto, and A. Concheiro, A comparison of gas-liquid chromatography, NMR spectroscopy and Raman spectroscopy for determination of the substituent content of general nonionic cellulose ethers, J. Pharmaceut. Biomed. Anal, 20 (1999) 373-383. 

The saturation, which is virtually proportional to the amount of polymer, is observed with approximately the same initial AT concentration for both materials but the amount of AT adsorbed on PSSO2GIU is about twice the amount of AT adsorbed on the same surface area of PSSO3 although the total substituent content is higher in PSSO3 than in PSS02Glu9. Furthermore the saturations determined in plasma system are approximately 8 times lower than the corresponding values obtained in purified system. This decrease was demonstrated to be essentially due to albumin which competes with AT for the adsorption on the polymer surface 0. 

Molecular weight Room temperature Substituent content Swelling Temperature... 

The enol content of a carboxylic acid is far less than that of an aldehyde or ketone and introduction of a halogen substituent at the a carbon atom requires a different set... 

Approximately half of the terminal D-mannosyl residues have pymvate present as 4,6-0-(l-carboxyethyhdene) substituents. The pymvate content has been shown to vary with culture conditions (337,338) and strains of A. campestris (339). The internal D-mannosyl residue is acetylated at the 0-6 position. 

The tautomeric equilibria of 5-hydroxy-3-aminopyrazoles 226 are affected by the substituent R" (Scheme 77) [76AHC(S1), p. 467]. While structure 226b is usually the major form, for some compounds of type 226 (R = COMe, COPh) the equilibrium content of 226c may reach 60% (74BSF291). 

CDCI3, DMSO-d, pyridine-ds), the equilibrium content of the ring-opened form 273 increases with increase in solvent polarity and electron-donor ability of the aryl substituent R. In the sohd, the cyclic tautomers are preferred as proven by IR spectroscopy (97ZOR418). 

The effect of the nature of the substituent at the acetylene bond is not so noticeable. Substitution reduces the C-3 activity due to polarization effects and steric factors. As aresult, in the cyclization with hydrazines and hydroxylamines an increase in the content of 5-substituted pyrazoles and isoxazoles is observed (81UK1252). As mentioned above, nonsymmetiic nitrogen-containing binucleophiles H2N—YH (Y = O, NMe, NPh) react with l-heteroalk-l-en-3-ynes in two alternative pathways by functions H2N and YH. 

The presence of organic acid substituents in exopolysaccharides increases the lipophilidty of the molecule. In addition, for some exopolysaccharides with relatively high organic acid contents, their interaction with cations and with other polysaccharides may be influenced. Several amino adds have also been found in bacterial exopolysaccharides, including serine and L-glutamic add (Figure 7.1). 

If the water content of the diazotization system is too high, the halogen atom in halogen-substituted mono- and dinitroanilines may be replaced by a hydroxy group in a bimolecular aromatic substitution. Analogous behaviour was observed in the diazotization of pentafluoroaniline, where the 4-fluoro substituent became hydrolysed (Brooke et al., 1965). As already mentioned in Section 2.1, this side reaction does not take place if the diazotization is conducted in a dichloromethane-aqueous sulfuric acid two-phase system in the presence of tetrakis[3,5-bis(trifluoromethyl)-phenyl]borate (Iwamoto et al., 1983a, 1984). 

The other structural parameters, such as the ester group content, the presence, nature, and position of substituents on monomer units, and the number and nature of comonomers, are of less importance and do not modify this classification of hnear polyesters. 

For sets nos. 1, 2, and 3 of Table XXVII, eq. (1) appears to hold for ionization of ortho substituted benzoic acids (f =. 048 —. 058), with Kj = Pi I= 1.6 . 1. This result is reasonable for field effects transmitted only throu the molecular cavity i.e., the lines of force do not pass through appreciable solvent of high dielectric constant (the solvent is presumably excluded by the close proximity of the CO2H center and the substituent) (36). It is further of interest that eq. (1) fails for the ionization of ortho substituted benzoic acids in solvents of high OH content (sets nos. 4, 5, and 6 of Table XXVII). 

Octachlorodibenzo-p-dioxin was photolyzed much more slowly than TCDD (Figure 1). The rate of dioxin photolysis increased as the number of substituent chlorine atoms decreased. Octachlorodibenzo-p-dioxin gave what seemed to be a series of chlorinated dioxins of decreasing chlorine content (20). 

If we consider the LOI values reported in Table 8, it can be clearly seen that the flame resistance of polyphosphazenes is very high and can reach values above 60 when halogenated phenoxy groups (e.g. 4-bromophenoxy) are attached to the polymer chain. However, enhancement of the carbon content in the materials (i.e. by increasing the percentage of organic substituents in the chain) induces a concurrent decrease in the flame resistance of POPs, which can be depressed to 23.4 in the case of poly[bis(4-/sopropylphenoxy)phos-phazene]. 

Huang et al. (7) suggested that the brevetoxin binding site lies in the hydro-phobic portion of the channel, and since PbTx-1 and PbTx-7 are also the most hydrophobic of the toxins, their potency may also be in part due to solubility considerations. In general, the more hydrophobic the toxin, the higher is its potency and ability to displace tritiated PbTx-3 from its specific binding site. It is our contention that substituent character on each toxin s K (type-1) or J (type-2) ring... 

The HM and LM pectins give two very different types of gels the mechanisms of stabilization of the junction zones in the two cases are described and few characteristics given. The different molecular characteristics (DE, distribution of methoxyl or acetyl substituents, neutral sugar content or rhamnose content) play an important role on the kinetic of gelation, mechanical properties of the gel formed and also on the experimental conditions to form the stronger gels. All these points were briefly discussed. 

An anaerobic bacterial enrichment cnltnre was used to examine the dechlorination of 2,3,4,5-tetrachlorobiphenyl that prodnced 2,3,5-trichlorobiphenyl exclusively. Although there was no alteration in the valnes of 5 C, compound-specific analysis of Arochlor 1268 showed that there was a trend for decreasing C abundance with increasing content of chlorine. This is consistent with dechlorination of the congeners with more chlorine substituents. 

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