Amines dissociation

A base is any material that produces hydroxide ions when it is dissolved in water. The words alkaline, basic, and caustic are often used synonymously. Common bases include sodium hydroxide (lye), potassium hydroxide (potash lye), and calcium hydroxide (slaked lime). The concepts of strong versus weak bases, and concentrated versus dilute bases are exactly analogous to those for acids. Strong bases such as sodium hydroxide dissociate completely while weak bases such as the amines dissociate only partially. As with acids, bases can be either inorganic or organic. Typical reactions of bases include neutralization of acids, reaction with metals, and reaction with salts ... 

Carbinolamines are chemically unstable and, in the case of tertiary amines, dissociate to generate the secondary amine and aldehydes as products or eliminate water to generate the iminium ion. The iminium ion, if formed, can reversibly add water to reform the carbinolamine or add other nucleophiles if present. If the nucleophile happens to be within the same molecule and five or six atoms removed from the electrophilic carbon of the iminium ion, cyclization can occur and form a stable 5- or 6-membered ring system. For example, the 4-imidazolidinone is a major metabolite of lidocaine, which is formed in vivo or can be formed upon isolation of the A -deethyl metabolite of lidocaine if a trace of acetaldehyde happens to be present in the solvent used for extraction (116,118) (Fig. 4.52). 

The triplet reaction of 2-nitrodibenzo[fc,primary amines (n-propylamine and benzylamine) was studied110 in polar and apolar solvents. In polar solvents, the irradiation results in the formation of two isomeric compounds, (alky-lamino)hydroxynitrodiphenyl ether andiV-(alkylamino)-2-nitrophenoxazine (equation 54). In apolar solvents, only the nitrophenoxazine is obtained. In polar solvents, the exciplex formed between the 2-n i trodi benzol h,e [ 1,4]dioxin triplet state and amines dissociates to the solvated radical ions, from which the diphenyl ether arises. 1-Nitrodibenzo[fr,e][l,4]dioxin is stable even on prolonged irradiation. 

Isocyanate Amine Dissociation constant of amine Reaction half-life (min)... 

Fatty amines can be synthesized by reacting alkylhalides with either ammonia or lower amines, from fatty acids and their derivatives (i.e., amides and ammonium salts), or by ammonolysis of fatty alcohols. Amines dissociate and reveal surface activity primarily under acidic conditions. Higher homologs, such as octadecylamine, are insoluble in water, but soluble in oil. 

This situation is reversed for amine dissociations in aqueous solutions, where the AH term does in fact dominate the TAS term [93,331]. Here the relevant dissociation process is... 

The rates (A i) indicate pronounced amine lability, in particular piperidine, while the ratio k-i/kg suggest a strong preference for CO binding. Comparison with porphyrin and phthalocyanin complexes indicates that CO dissociation rates are relatively insensitive to the nature of the in-plane ligand unlike, those of amine dissociation k which vary from 1020 s (OMBP) to 0.50 S (phthalocyanine). The binding of CO to [Fe(TAAB)L2] + is very poor in contrast to the above results which may reflect the enormous number of differences in the structure and electronic features of TAAB relative to OMBP and other related chelates. However, CO dissociation does not occur readily, while dimethylglyoxime complexes are even more... 

The nature of the fimctional groups of the macroligands is also of great importance. For instance, monomeric and polymeric amines dissociate the [Rh(CO)2RS]2 dimer complex in contrast to thiols that yield addition products. Similarly, the nature of the solvent affects chain flexibility and long-range action. For example, the Co complex with a crosslinked PS polymer has a Co L composition of 1 1 (L-monomer unit) in weakly swelling n-hexadecane, whereas a thermodynamically stable 1 2 complex forms in xylene. This observation may be a result of the fact that a PS support is glassy at 70°C in n-hexadecane and gum-like in xylene. 

The Kent-Eisenberg model assumes all activity coefficients and fiigacity coefficients to be 1.0 (i.e., ideal solutions and ideal gases), and forces a fit between experimental and predicted values by treating two of the reaction equilibrium constants as variables. The reactions so treated are the amine dissociation reaction (equation 2-6) and the carbamate formation reaction (equation 2-7). Since tertiary amines do not form carbamates, a modified approach is required in developing a generalized correlation for these amines. Jou et al. (1982) describe such an approach for the correlation of H2S and CO2 solubilities in aqueous MDEA solutions. 

The reaction of ammonia and amines with esters follows the same general mech anistic course as other nucleophilic acyl substitution reactions (Figure 20 6) A tetrahe dral intermediate is formed m the first stage of the process and dissociates m the second stage... 

All these reactions proceed by nucleophilic addition of the amine to the carbonyl group Dissociation of the tetrahedral intermediate proceeds m the direction that leads to an amide... 

Butyrolactone reacts rapidly and reversibly with ammonia or an amine forming 4-hydroxybutyramides (175), which dissociate to the starting materials when heated. At high temperatures and pressures the hydroxybutyramides slowly and irreversibly dehydrate to pyrroHdinones (176). A copper-exchanged Y-2eohte (177) or magnesium siUcate (178) is said to accelerate this dehydration. 

Retardation of the reaction rate by the addition of dimethyl sulfide is in accord with this mechanism. Borane—amine complexes and the dibromoborane—dimethyl sulfide complex react similarly (43). Dimeric diaLkylboranes initially dissociate (at rate to the monomers subsequentiy reacting with an olefin at rate (44). For highly reactive olefins > k - (recombination) and the reaction is first-order in the dimer. For slowly reacting olefins k - > and the reaction shows 0.5 order in the dimer. 

The free maleic acid content in maleic anhydride is determined by direct potentiometric titration (166). The procedure involves the use of a tertiary amine, A/-ethylpipetidine [766-09-6J, as a titrant. A tertiary amine is chosen as a titrant since it is nonreactive with anhydrides (166,167). The titration is conducted in an anhydrous solvent system. Only one of the carboxyhc acid groups is titrated by this procedure. The second hydrogen s dissociation constant is too weak to titrate (166). This test method is not only used to determine the latent acid content in refined maleic acid, but also as a measure of the sample exposure to moisture during shipping. 

Bond dissociation energies (BDEs) for the oxygen—oxygen and oxygen— hydrogen bonds are 167—184 kj/mol (40.0—44.0 kcal/mol) and 375 kj/mol (89.6 kcal/mol), respectively (10,45). Heats of formation, entropies, andheat capacities of hydroperoxides have been summarized (9). Hydroperoxides exist as hydrogen-bonded dimers in nonpolar solvents and readily form hydrogen-bonded associations with ethers, alcohols, amines, ketones, sulfoxides, and carboxyhc acids (46). Other physical properties of hydroperoxides have been reported (46). 

The addition of alkyl haUdes to phosphines is analogous to the reactions with amines. Because primary phosphonium salts are highly dissociated, the reaction proceeds to the tertiary or quartemary salts. 

DMAMP and AMP are among the strongest amines commercially available. The dissociation constants of these materials appear in Table 2. AH alkan olamines have slight amine odors in the Hquid state the soHds are nearly odorless. 

The hterature suggests that more than one mechanism may be operative for a given antiozonant, and that different mechanisms may be appHcable to different types of antiozonants. All of the evidence, however, indicates that the scavenger mechanism is the most important. All antiozonants react with ozone at a much higher rate than does the mbber which they protect. The extremely high reactivity with ozone of/)-phenylenediamines, compared to other amines, is best explained by their unique abiUty to react ftee-tadicaHy. The chemistry of ozone—/)-PDA reactions is known in some detail (30,31). The first step is beheved to be the formation of an ozone—/)-PDA adduct (32), or in some cases a radical ion. Pour competing fates for dissociation of the initial adduct have been described amine oxide formation, side-chain oxidation, nitroxide radical formation, and amino radical formation. 

Appllca.tlons. MCA is used for the resolution of many classes of chiral dmgs. Polar compounds such as amines, amides, imides, esters, and ketones can be resolved (34). A phenyl or a cycloalkyl group near the chiral center seems to improve chiral selectivity. Nonpolar racemates have also been resolved, but charged or dissociating compounds are not retained on MCA. Mobile phases used with MCA columns include ethanol and methanol. 

Dissociation extraction is the process of using chemical reac tion to force a solute to transfer from one liquid phase to another. One example is the use of a sodium hydroxide solution to extract phenolics, acids, or mercaptans from a hydrocarbon stream. The opposite transfer can be forced by adding an acid to a sodium phenate stream to spring the phenolic back to a free phenol that can be extrac ted into an organic solvent. Similarly, primary, secondary, and tertiary amines can be protonated with a strong acid to transfer the amine into a water solution, for example, as an amine hydrochloride salt. Conversely, a strong base can be added to convert the amine salt back to free base, which can be extracted into a solvent. This procedure is quite common in pharmaceutical production. 

Delphonine shows an unusually high basic dissociation constant, and that of aconine is only a little less. In the case of tertiary vinyl cyclic amines, which prove to be unexpectedly strong bases, Adams and Mahan suggested that they exist in solution as equilibrium mixtures consisting of the tertiary unsaturated base and a quaternary arrangement in which the double bond has moved to the nitrogen, which may be represented thus —. . . +. . . +... 

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