Alkyl groups with /3-hydrogens

Consider first the electronic effect of alkyl groups versus hydrogen atoms attached to C=0 Recall from Section 17 2 that alkyl substituents stabilize C=0 making a ketone carbonyl more stable than an aldehyde carbonyl As with all equilibria factors... 

Steric and inductive effects determine the rate of formation of the pentacovalent siUcon reaction complex. In alkaline hydrolysis, replacement of a hydrogen by alkyl groups, which have lower electronegativity and greater steric requirements, leads to slower hydrolysis rates. Replacement of alkyl groups with bulkier alkyl substituents has the same effect. Reaction rates decrease according to ... 

Carboxylic esters 1, having an O-alkyl group with a /3-hydrogen, can be cleaved thermally into the corresponding carboxylic acid 2 and an alkene 3. This reaction often is carried out in the gas phase generally the use of a solvent is not necessary. 

Very interestingly, all cyanohydrins (61h-m) which are substituted with one phenyl group and one less bulky alkyl group or hydrogen atom do not form inclusion complex with 4. However, the cyanohydrins which are substituted with two alkyl groups (62a-c) or with one alkyl group and one hydrogen atom (62d-f) formed complex with 4 and were resolved.27 3... 

Table 2. Electric fields (F), electrostatic potentials (and hydrogen bond donating parameters (a) for molecules with alkyl groups as hydrogen bond donors...

M2+02 (M = Mg, Ca, Sr) coordinatively unsaturated pairs are able to abstract a hydrogen ion from acetylenic hydrocarbons following the reaction path shown in Scheme 4 (—, surface plane R, alkyl group), with formation... 

The hydrogen on carbon 3 on the thiophene or the pyrrole ring was replaced with an alkyl group with at least four carbon atoms in it. The resulting polymer, when doped, has a comparable conductivity to its parent polymer whilst be able to melt and it is soluble. A water soluble version of these polymers has been produced by placing carboxylic acid group or sulphonic acid group on the alkyl chains. 

In contrast, Schrock carbenes are electron deficient [10 to 16 valence electrons (VE)] early transition metal complexes with the metal atom in a high oxidation state and carbene substituents that are limited to alkyl groups and hydrogen [131]. Their bonding situation can be described in terms of the interaction of a triplet carbene with a triplet metal fragment resnlting in a covalent double bond [132], Tantalum complexes like [(np)3Ta=CHBu ] and [Cp2(Me)Ta=CH2] are representative of Schrock carbenes. 

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