Conjugate bases stability

Strong acid pKa = 0.63 Weak Conjugate base (stabilized)... 

Summary The relationship between acidity and conjugate base stability for acetic acid, CH3-C ... 

Resonance, The second factor for comparing conjugate base stability is resonance. To illustrate the role of resonance in charge stability, let s consider the structures of ethanol and acetic add ... 

Enolate ion (Section 18 6) The conjugate base of an enol Enolate ions are stabilized by electron delocalization... 

Carbanions derived from carbonyl compoimds are often referred to as etiolates. This name is derived from the enol tautomer of carbonyl compounds. The resonance-stabilized enolate anion is the conjugate base of both the keto and enol forms of carbonyl... 

With a p fa of 16, cyclopentadiene is only a slightly weaker acid than water (pA a = 15.7). It is much more acidic than other hydrocarbons—its for ionization is 10 ° times greater than acetylene, for example—because its conjugate base is aromatic and stabilized by electron delocalization. 

Electron delocalization in an acid, or its conjugate base can have a large impact on both stability and reactivit Consider the following acids and their conjugate bases. 

The pKa of 1,3-cyclopentadiene is 15, making it more acidic than water, as well as more acidic than almost any other hydrocarbon. This unusual acidity is presumably due to resonance stabilization of the conjugate base, which can be drawn as a hybrid of five resonance contributors. 

The two-step procedure includes formation of a N-substituted phthalimide 3, and its subsequent cleavage to the primary amine 5. Phthalimide (which can be obtained from reaction of phthalic acid with ammonia) shows NH-acidity, since the negative charge of the phthalimide anion (the conjugated base) is stabilized... 

The acidity of acetone and other compounds with C=0 bonds is due to the fact that the conjugate base resulting from loss of H+ is stabilized by resonance. In addition, one of the resonance forms stabilizes the negative charge by placing it on an electronegative oxygen atom. 

The bottom portion of Table 8.1 consists of very weak acids pK. above 17). In most of these acids, the proton is lost from a carbon atom, and such acids are known as carbon acids. The pa s values for such weak acids are often difficult to measure and are known only approximately. The methods used to determine the relative positions of these acids are discussed in Chapter 5. The acidity of carbon acids is proportional to the stability of the carbanions that are their conjugate bases (see p. 227). 

Are there any inductive effects (electronegative atoms or alkyl groups) that stabilize or destabilize any of the conjugate bases ... 

Resonance Neither of the conjugate bases is stabilized by resonance. 

The conjugate base of phenol is stabilized by resonance. This explains why phenolic protons are more acidic than typical alcoholic protons. 

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