Basicity of functional groups

Photoinduced proton transfer may be generated through the large variation in acidity or basicity of functional groups in the excited states of specific structures [8.226] and lead to photoinduced pH jumps [8.227,8.228]. Changes of optical properties by tautomerisation in the excited state [8.229] occur, for instance, in the fluorescent states of bipyridyl diols [8.230a] and form the basis of a proton transfer laser process [8.230b]. 

Studies on the ability of a cyclopropane to conjugate have involved a wide variety of approaches including spectroscopic, thermochemical, structural and theoretical examinations. Two overall thrusts are apparent in the reported work. One approach has been to investigate the impact of a cyclopropyl substituent on the properties of an attached functional group or molecule. Typically, techniques used include measurement of the substituent parameters of a cyclopropyl group, determination of the acidity or basicity of functional groups attached to a cyclopropane, or measurement of the impact of a cyclopropyl substituent on the absorption spectrum of an attached chromophore ... 

A. The Basicity of Functional Groups Directly Bonded to Silicon, R3SiX (X = NR9,... 

Further revision in thinking about acidity and basicity of functional groups, and reinforcement of expected piCa values for functional groups. Amino acids are particularly important. 

The measure of acidity and basicity of functional groups of amino acids are the dissociation constants. The dissociation constant Xj describes the acidity of the a-carboxyl group of glycine, as shown by the following reaction ... 

It was noted that the content of functional groups on the surface of studied A1,03 was 0,92-10 mol/g of acid character for (I), FOS-IO mol/g of basic character for (II). The total content of the groups of both types was 1,70-lO mol/g for (III). The absence of appreciable point deviations from a flat area of titration curves in all cases proves simultaneously charges neutralization character on the same adsoi ption centers and non-depending on their density. The isoelectric points of oxide surfaces have been detenuined from titration curves and have been confirmed by drift method. 

It is possible to calculate a number of different kinds of "effective" crosslink densities. Bauer et al have used a quantity they termed the "elastically effective crosslink density " (Cel) correlate cure with solvent resistance and other physical properties of coatings (7-10). The correlation was basically empirical. Formally, the is a calculation of the number of functional groups attached to the infinite network for which there are at least two other paths out to the network on the given polymer or crosslinker. Thus, chains with only one or two paths to the infinite network are excluded. The following expression can be written for... 

The protection-deprotection reaction sequences constitute an integral part of organic syntheses such as the preparation of monomers, fine chemicals, and reaction intermediates or precursors for pharmaceuticals. These reactions often involve the use of acidic, basic or hazardous reagents and toxic metal salts [30], The solvent-free MW-accelerated protection/deprotection of functional groups, developed during the last decade, provides an attractive alternative to the conventional cleavage reactions. 

Absorbents based on a variety of amines are by far the most common. Amines that have been used include monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), diisopropanolamine (DIPA), methyl diethanolamine (MDEA), and digly-colamine (DGA). C02 is typically absorbed at 80-140°F temperature and up to 1000 psig pressure by chemically reacting with the basic amine functional group in the absorbent, for example, primary amine, MEA, reacts with C02 by the following reaction forming a carbamate salt ... 

Preparation of benzotriazolyl derivatives substituted at N-l (or N-2) with variety of functional groups is described in detail in Sections 5.01.5 and 5.01.8. The basic strategy starts from a reaction of benzotriazole with an electrophile. In most cases, the reaction produces a mixture of benzotriazol-l-yl and benzotriazol-2-yl derivatives that is not difficult to separate. Further modification of the substituent in subsequent steps leads to the desired product. 

Reactions may be initiated by protonation of functional groups of a substrate to form a reactive intermediate. The tendency for protonation decreases with decreasing basicity, i.e., with decreasing pKa of the conjugated acid. Qualitatively, the tendency to... 

Strong through-space interactions are possible in medium rings. Such interactions have been discovered in certain alkaloids like cryptopine and protopine, which are characterized by atypical properties of their functional groups like low basicity of amino groups and low carbonyl reactivity of carbonyl groups. 

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