Primary amines, inhibition

Satchell and Satchell" reported a kinetic study on the aminolysis of p-nitrophenyl isothiocyanate with primary amines and anilines in diethyl ether and isooctane as solvents. The detailed analysis reveals that the aminolysis occurs via a zwitterionic intermediate, T , which undergoes subsequent proton transfer catalyzed by a second amine molecule (equation 12). Added carboxylic acids form inactive 1 2 amine-acid complexes with strong basic amines and inhibit aminolysis, but with weak bases the acids form only a negligible amount of complex and they catalyze the aminolysis. 

Amantadine hydrochloride (1-adamantanamine hydrochloride) is a symmetric, tricyclic, primary amine that inhibits penetration of RNA viral particles into the host cell (19). It also inhibits the early stages of viral replication by blocking the uncoating of the viral genome and the transfer of nucleic acid into the host... 

Cyclohexylamine is miscible with water, with which it forms an azeotrope (55.8% H2O) at 96.4°C, making it especially suitable for low pressure steam systems in which it acts as a protective film-former in addition to being a neutralizing amine. Nearly two-thirds of 1989 U.S. production of 5000 —6000 t/yr cyclohexylamine serviced this appHcation (69). Carbon dioxide corrosion is inhibited by deposition of nonwettable film on metal (70). In high pressure systems CHA is chemically more stable than morpholine [110-91-8] (71). A primary amine, CHA does not directiy generate nitrosamine upon nitrite exposure as does morpholine. CHA is used for corrosion inhibitor radiator alcohol solutions, also in paper- and metal-coating industries for moisture and oxidation protection. 

Rifamycin S also undergoes conjugate addition reactions to the quinone ring by a variety of nucleophiles including ammonia, primary and secondary amines, mercaptans, carbanions, and enamines giving the C-3 substituted derivatives (38) of rifamycin SV (117,120,121). Many of the derivatives show excellent antibacterial properties (109,118,122,123). The 3-cycHc amino derivatives of rifamycin SV also inhibit the polymerase of RNA tumor vimses (123,124). 

Methylene chloride is one of the more stable of the chlorinated hydrocarbon solvents. Its initial thermal degradation temperature is 120°C in dry air (1). This temperature decreases as the moisture content increases. The reaction produces mainly HCl with trace amounts of phosgene. Decomposition under these conditions can be inhibited by the addition of small quantities (0.0001—1.0%) of phenoHc compounds, eg, phenol, hydroquinone, -cresol, resorcinol, thymol, and 1-naphthol (2). Stabilization may also be effected by the addition of small amounts of amines (3) or a mixture of nitromethane and 1,4-dioxane. The latter diminishes attack on aluminum and inhibits kon-catalyzed reactions of methylene chloride (4). The addition of small amounts of epoxides can also inhibit aluminum reactions catalyzed by iron (5). On prolonged contact with water, methylene chloride hydrolyzes very slowly, forming HCl as the primary product. On prolonged heating with water in a sealed vessel at 140—170°C, methylene chloride yields formaldehyde and hydrochloric acid as shown by the following equation (6). 

The method can be applied to most phenols substituted in the ortho or meta position and to phenols substituted in the para position by OH or OCH3 groups most other substituents in the para position inhibit the reaction. Aromatic primary amines unsubstituted in the para position interfere and must be removed if possible before commencing the determination by extraction with acid. 

The disadvantages associated with HRP are several. The enzyme only contains two available primary e-amine groups—extraordinarily low for most proteins—thus limiting its ability to be activated with amine-reactive heterobifunctionals. HRP is sensitive to the presence of many antibacterial agents, especially azide. It also is reversibly inhibited by cyanide and sulfide (Theorell, 1951). Finally, while the enzymatic activity of HRP is extremely high, its useful lifespan or practical substrate development time is somewhat limited. After about an hour of substrate turnover, in some situations its activity can be decreased severely. 

The oxidation of primary and secondary alcohols in the presence of 1-naphthylamine, 2-naphthylamine, or phenyl-1-naphthylamine is characterized by the high values of the inhibition coefficient / > 10 [1-7], Alkylperoxyl, a-ketoperoxyl radicals, and (3-hydroxyperoxyl radicals, like the peroxyl radicals derived from tertiary alcohols, appeared to be incapable of reducing the aminyl radicals formed from aromatic amines. For example, when the oxidation of tert-butanol is inhibited by 1-naphthylamine, the coefficient /is equal to 2, which coincides with the value found in the inhibited oxidation of alkanes [3], However, the addition of hydrogen peroxide to the tert-butanol getting oxidized helps to perform the cyclic chain termination mechanism (1-naphthylamine as the inhibitor, T = 393 K, cumyl peroxide as initiator, p02 = 98 kPa [8]). This is due to the participation of the formed hydroperoxyl radical in the chain termination ... 

Another situation is observed when salts or transition metal complexes are added to an alcohol (primary or secondary) or alkylamine subjected to oxidation in this case, a prolonged retardation of the initiated oxidation occurs, owing to repeated chain termination. This was discovered for the first time in the study of cyclohexanol oxidation in the presence of copper salt [49]. Copper and manganese ions also exert an inhibiting effect on the initiated oxidation of 1,2-cyclohexadiene [12], aliphatic amines [19], and 1,2-disubstituted ethenes [13]. This is accounted for, first, by the dual redox nature of the peroxyl radicals H02, >C(0H)02 and >C(NHR)02 , and, second, for the ability of ions and complexes of transition metals to accept and release an electron when they are in an higher- and lower-valence state. 

Few studies have systematically examined how chemical characteristics of organic reductants influence rates of reductive dissolution. Oxidation of aliphatic alcohols and amines by iron, cobalt, and nickel oxide-coated electrodes was examined by Fleischman et al. (38). Experiments revealed that reductant molecules adsorb to the oxide surface, and that electron transfer within the surface complex is the rate-limiting step. It was also found that (i) amines are oxidized more quickly than corresponding alcohols, (ii) primary alcohols and amines are oxidized more quickly than secondary and tertiary analogs, and (iii) increased chain length and branching inhibit the reaction (38). The three different transition metal oxide surfaces exhibited different behavior as well. Rates of amine oxidation by the oxides considered decreased in the order Ni > Co >... 

Nevertheless, the results observed for the reactions of o- and p-11 uoronitrobenzenes with propylamines demonstrate that (a) the dichotomy is not only observed when comparing primary with secondary amines (b) the origin is not due to primary steric effects (c) when there is no artho-n. m group the decrease in rate for the bulky amine is greater (d) the diminution in rate is due to an inhibition effect in the base-catalysed decomposition. 

The catalysed two-phase alkylation of carboxamides has the advantages of speed and simplicity over the traditional procedures and provides a valuable route to secondary and tertiary amines by hydrolysis or reduction of the amides, respectively. The procedure appears to be limited, however, to reactions with primary haloalkanes and dialkyl sulphates, as secondary haloalkanes are totally unreactive [6, 7]. The use of iodoalkanes should be avoided, on account of the inhibiting effect of the released iodide ion on the catalyst. Also, the A-alkylation reaction is generally susceptible to steric effects, as seen by the low yields in the A -cthylation of (V-/-butylacetamide and of A-ethylpivalamide [6]. However, the low steric demand of the formyl group permits A,A-dialkylation and it is possible to obtain, after hydrolysis in 60% ethanolic sulphuric acid, the secondary amines having one (or, in some cases, two) bulky substituent(s) [7]. 

Under batch conditions, methylations with DMC must necessarily be run in sealed autoclaves, given its boiling point (90°C) and the reaction temperature (>160°C). Batch methylations with DMC can be performed on a number of different substrates and, under such conditions, the reaction mechanism can be conveniently investigated in fact, the sampling of the reaction mixture at different conversions, and the identihcation of possible intermediates (see later) is easier with respect to CF-processes. For compounds that are susceptible to multiple methylation, the results are of special interest, since methylation with DMC totally inhibits multiple substimtion in both N- and C-alkylation, for primary aromatic amines and for CH2-active compounds, respectively. 

Antidepressants of this class, such as moclobemide, have a high selectivity and affinity for MAO-A. Flowever, unlike the MAOIs, the RIMAs are reversible inhibitors of the enzyme and can easily be displaced from the enzyme surface by any primary amine which may be present in the diet. This means that the dietary amines are metabolized by MAO in the wall of the gastrointestinal tract while the enzyme in the brain and elsewhere remains inhibited. Thus the RIMAs have brought the MAOIs back into use as antidepressants in general practice. It is now evident that the RIMAs are not as potent as most currently available antidepressants. 

Imipramine is the primary representative of typical tricyclic antidepressants. It acts by blocking the mechanism of renptake of biogenic amines. It does not inhibit MAO activity. Imipramine lessens sadness, lethargy, improves mood, and improves the mental and overall tone of the body. It is nsed in depression of varions etiology accompanied by motor cinmsiness and ennresis in children and Parkinson s disease. Primary synonyms of this drag are tofranil, snrplix, imizin, melipramin, and others. 

---