Proton donor groups

It follows from the preceding discussion that the unbranched H bond can be regarded as a 3-centre 4-electron bond A-H B in which the 2 pairs of electrons involved are the bond pair in A-H and the lone pair on B. The degree of charge separation on bond formation will depend on the nature of the proton-donor group AH and the Lewis base B. The relation between this 3-centre bond formalism and the 3-centre bond descriptions frequently used for boranes, polyhalides and compounds of xenon is particularly instructive and is elaborated in... 

This type of tautomerism pertains to azole systems which contain exo-cyclic amino, hydroxy, thiol, and other proton donor groups. 

T. Deuterium isotope effects on 13 C chemical shifts In the studies of proton transfer equilibrium of Schiff bases, the most informative are deuterium isotope effects measured for carbons bonded with proton donor groups (C-2 or C-7 for gossypol derivatives). For imines in which... 

Hansen et al.52 measured the deuterium isotope effects for the Schiff base being a derivative of racemic gossypol [7]. The high negative value of deuterium isotope effect observed at carbon C-7 linked with proton donor group (—190 — 240 ppb), solvent and temperature independent, clearly indicated the existence of this compound as enamine-enamine tautomer. 

Compounds containing proton donor groups such as O—H and N—H can be involved in intra- or... 

The detrimental effect of the reactive proton-donor group in the [AMIM] ion was further confirmed by the use of an ionic liquid with the proton at the C2 position replaced by a methyl group. The palladium catalyst in [BDMIM]PF6 showed high activity and selectivity in a biphasic system that allowed reaction with multiple recycles and little loss of activity. 

Hydrogen bonding can occur in any system containing a proton donor group (X—H) and a proton acceptor... 

The strength of the hydrogen bond is at a maximum when the proton donor group and the axis of the lone pair orbital are collinear. The strength of the bond decreases as the distance between X and Y increases. 

In the system epoxide (epoxy resin) — anhydride, we can thus expect the presence of anhydride, epoxy- and proton donor groups. In their study of the reaction mechanism, Fisch and Hofmann 20 22-24) proposed a sequence of reactions leading to the crosslinking of epoxy resins or to the formation of linear polyesters. The first step is the reaction of the anhydride with hydroxyl groups giving a monoester (Eq.(l))... 

Pre-adsorption of polymers causes an increase in the adsorption of metal cations at low pH values (Figures 3 and 4). There is a difference in the effects of PVA (with COH functionalities) and PEG (C-O-C) because the adsorption of PEG diminishes the plateau adsorption of Cd(II) (Figure 4) in contrast to PVA (Figure 3). This can be caused by the absence of proton-donor groups in PEG reducing the probability of ion-exchange reactions, and diminishes the number of accessible surface silanols as proton-donors because of the strong interaction... 

One exception to the absence of site-competition delocalization on alumina is noted for solutes with acidic substituents. These are held quite strongly on alumina, eind it is believed this is due to the direct interaction of these proton-donor groups with surface oxide groups on alumina. Thus, for this situation the requirements for site competition are met, and the... 

Different selectivity due to presence of proton donor group. 

The Cl atom in CH3CI can unsurprisingly act as a proton acceptor when paired with formic acid. In conjunction with this particular interaction, one of the H atoms of methyl chloride can curl around and approach an oxygen atom of HCOOH Several geometries of the dimer which contain this second potential H-bond are illustrated in Fig. 2.16. The notation lists the proton donor group of the formic acid (which can be either the OH or CH), followed by the proton acceptor oxygen ( =0 or 0). 

Class of compounds having proton donor groups... 

In the case of the dichloride salt, the smaller size of the chloride anion (comparatively to that of the perchlorate) and its stronger proton acceptor properties allow it to establish intermolecular bonds with all the proton-donor groups occurring in the vicinity of organic counterions. 

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