Carboxyl group, alkyl stabilization

Several innovations have significantly extended the scope and synthetic utility of the classical Michaelis-Becker phosphonoacetate preparation. Eor example, the coupling of the Michaelis-Becker and Homer-Wadsworth-Emmons reactions for the synthesis of a-substituted acrylic acids represents a useful modification. According to Scheme 8.10, Michaelis-Becker alkylation of a dialkyl phosphite with a haloacetic acid in the presence of 3 eq of a base (one to neutralize the carboxyl group, one to form the phosphite conjugate base, and one to deprotonate the initially formed alkylation product) leads to the phosphoryl-stabilized anion directly. Treatment of the anion... 

Skinner and Snelson ) have measured the heats of hydrogenation of two pairs of cisjtrans isomers of compounds contain-ing an olefinio and an acetylenic bond (Table 5). For the dec-en-ynes, and pent-en-ynes the cis isomers are slightly more stable than the trans isomers. The difference in the heat of hydrogenation is small, and the errors attached to the results aire large, so that tbe order of stability may not be as it appears. However, it appears that the steric requirements of the acetylenic group are less than the alkyl or carboxylic groups. 

On the other hand, copolymers of maleic acid with various vinyl monomers had been investigated in studying the influence of local charge density on polyelectrolyte properties, and some alternating copolymers of maleic acid with n-alkyl vinyl ethers were found to undergo the conformational transitions from the compact form to the extended coil upon ionization of primary carboxyl groups in maleic acid. " The hydrophobic interaction seems to be responsible for stabilization of the compact form. Viscometric, potentiometric and calorimetric measurements have been used to study the transition mechanisms. 

Salts and esters of carboxylic acids are called carboxylates. When a carboxyl group is deprotonated, its conjugate base, a carboxylate anion is formed. Carboxylate ions are resonance stabilized and this increased stability makes carboxylic acids more acidic than alcohols. Carboxylic acids can be seen as reduced or alkylated forms of the Lewis acid carbon dioxide under some circumstances they can be decarboxylated to yield carbon dioxide. 

A thermal stabilizer is used to improve the chemical stability of PVC at processing temperatures. Many highly effective PVC thermal stabilizers are already known [16,23-29], but their action mechanism is not yet completely established [13,30-33]. Frye and Horst [34,35] suggest the following mechanism for an organic soap type heat stabilizer where chlorine atoms in labile positions are replaced by the alkyl carboxylate group as follows ... 

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