Conjugate acid of methylamine

Methylammonium ion, being the conjugate acid of methylamine, is a weak acid (Reaction 6-28). Chloride is the conjugate base of HC1, a strong acid. In other words, Cl- has virtually no tendency to associate with H+, or else HC1 would not be a strong acid. Methylammonium chloride is acidic because methylammonium ion is an acid and Cl is not a base. 

The conjugate acid of methylamine has a pXa of approximately 10.6. Based on the Henderson-Hasselbalch equation (Equation 9.1 in Chapter 9), calculate the percentage of methylamine that is not protonated (not in the form of its conjugate acid) at pH 7.4, the same as blood. 

The conjugate acid of ammonia is ammonium ion (NH4 ), which has = 5.6 X 10 ° (p/fa = 9.3). The conjugate acid of methylamine is methylammoifium ion (CH3NH3 ), which has = 2 X 10 (pATa = 10.7). The more basic the amine, the weaker is its conjugate acid. Methylamine is a stronger base than ammonia methylammonium ion is a weaker acid than ammonium ion. 

In acid the imide undergoes cleavage to give a dicarboxyUc acid and the conjugate acid of methylamine. 

The chemical formula for the conjugate acid of methylamine is usually written CH3NH3+. 

In contrast to strong bases, a weak base ionizes only partially in dilute aqueous solution to form the conjugate acid of the base and hydroxide ion. The weak base methylamine (CH3NH2) reacts with water to produce an equilibrium mixture of CH3NH2 molecules, CH3NH3+ ions, and OH ions. 

Draw the conjugate base of nitric acid. Is this base strong enough to induce an E2 reaction with an alkyl halide What is the conjugate base of methylamine Is it strong enough to induce an E2 reaction ... 

D. The pK s of the conjugate acids of aniline and methylamine are 4.6 and 10.7, respectively. What accounts for the greater acidity of the conjugate acid of aniline ... 

Formal oxidation of pyrrolidine to the succinimide stage affords a series of compounds used as anticonvulsant agents for treatment of seizures in petit mal epilepsy. Knoevnagel condensation of benzaldehyde with ethyl cyanoacetate affords the unsaturated ester, 9. Conjugate addition of cyanide ion leads to the di-nitrile ester (10). Hydrolysis in mineral acid affords the succinic acid (11), presumably by decarboxylation of the intermediate tricarboxyllie acid. Lactamization with methylamine gives phensuximide (12). ... 

The p Ta of cyclohexylamine (10.6) is typical of an aliphatic amine (methylamine also has p/fa 10.6). Aniline is a much weaker base (the smaller the p Ta, the weaker the base) than cyclohexylamine. This is a combination of an inductive effect and a resonance effect, which reinforce each other. The phenyl ring provides an electron-withdrawing inductive effect that destabilizes the conjugate acid. More important, though, is the resonance effect that stabilizes the uncharged amine. 

Acetate is a base because it can accept a proton to make acetic acid. Methylammonium ion is an acid because it can donate a proton and become methylamine. Acetic acid and the acetate ion are said to be a conjugate acid-base pair. Methylamine and methylammonium ion are likewise conjugate. Conjugate acids and bases are related to each other by the gain or loss of one H+. 

Amines are weak bases, and ammonium ions are weak acids. The parent of all amines is ammonia, NH3. When a base such as methylamine reacts with water, the product is the conjugate acid. That is, methylammonium ion produced in Reaction 6-27 is a weak acid ... 

Arrange the following bases in order of increasing strength on the basis of the pKa values of their conjugate acids, which are given in parentheses (a) ammonia (9.26) (b) methylamine (10.56) ... 

Methylamine on the left hand side of the equation is called the free base, whereas the methyl ammonium ion formed on the right hand side is called the conjugate acid. The extent of ionisation or dissociation in the equilibrium reaction is defined by the equilibrium constant (Keq) ... 

The synthesis of unnatural (+)-mesembrine (387) through the asymmetric synthesis of methyl (i )-l-[(3,4-dimethoxy)phenyl]-4-oxocyclohex-2-enyl acetate (390) by cycloaddition of enantiomerically pure vinyl sulfoxide with dichloroketene has been performed 189) (Scheme 43). Vinyl sulfoxide 388 [prepared by conjugate addition of enantiopure acetylenic sulfoxide with (3,4-dimethoxy)phenylcopper] reacted with trichloroacetyl chloride in the presence of freshly prepared zinc-copper couple in THF at 0°C to produce a mixture of mono- and dichloro lactones 389. Reduction of 389 with zinc in acetic acid followed by cyclization and methylation afforded methyl IR-[(3,4-dimethoxy)phenyl]-4-oxocyclohex-2-enyl acetate (390), treatment of which with methylamine brought about amidation and concomitant intramolecular Michael addition to provide 2-oxo-mesembrine (391). Successively, 391 was transformed to (+)-mesembrine (387) in 79% yield (three steps ketalization of an oxo group, reduction of lactam, and deketali-zation)(/S9). 

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