Dimethyl amine, ionization

Several gases are used in Cl ionization methane, propane, isobutane, hydrogen, ammonia, water, tetramethyl silane, or dimethyl amine. The Cl ion source is similar to the El source but is designed to have an ionization chamber. In positive chemical ionization, the ion source is filled with a reagent gas which is ionized to create a species of the proton donator type that can form a... 

The acidic properties of l-methyl-4-dimethylamino-5-nitro-2-oxo-pyrimidine (p/fa 9.04), a molecule with no ionizable proton, have been traced to the structure 30, which is the anion of a hydrate,50 The acidic properties (pKa 10.57) of the corresponding primary amine, 5-nitro-cytosine,51 probably depend on a similar hydration. In solution, 1,3-dimethyl-5-nitrouracil adds water across the 5,6 (C=C) double bond at pH 9.5, but not at neutrality.52... 

The ionization constants,331 NMR spectra,174 and mass spectra1227 of representative amino-1,6-naphthyridines have been compared with those of related amino derivatives. Complexes of l,6-naphthyridin-2-amines with tetracyanoquinodi-methane have been studied.416 4-(3-Dimethylamino-l-methylpropylamino)-l,6-naphthyridine showed significant antimalarial activity.236 X-ray analyses of a number of 5-amino-1,6-naphthyridines have been reported in connection with their antibacterial activities for example, ethyl 5-amino-7-benzylseleno-8-cyano-4-(fur-2-yl)-l,2-dimethyl-l,4-dihydro-l,6-naphthyridine-3-carboxylate (10) proved to be a mixture of two symmetric conformers in each crystal 772 the other related compounds appear to be composed of single conformers.558,560 562 759 781 1289... 

Sections 3.3.1 and 4.2.1 dealt with Bronsted acid/base equilibria in which the solvent itself is involved in the chemical reaction as either an acid or a base. This Section describes some examples of solvent effects on proton-transfer (PT) reactions in which the solvent does not intervene directly as a reaction partner. New interest in the investigation of such acid/base equilibria in non-aqueous solvents has been generated by the pioneering work of Barrow et al. [164]. He studied the acid/base reactions between carboxylic acids and amines in tetra- and trichloromethane. A more recent compilation of Bronsted acid/base equilibrium constants, determined in up to twelve dipolar aprotic solvents, demonstrates the appreciable solvent influence on acid ionization constants [264]. For example, the p.Ka value of benzoic acid varies from 4.2 in water, 11.0 in dimethyl sulfoxide, 12.3 in A,A-dimethylformamide, up to 20.7 in acetonitrile, that is by about 16 powers of ten [264]. 

Many reactions become possible only in such superbasic solutions, while others can be carried out under much milder conditions. Only some examples of preparative interest (which depend on the ionization of a C—H or N—H bond) will be mentioned here. The subsequent reaction of the resulting carbanion may involve electrophilic substitution, isomerization, elimination, or condensation [321, 322]. Systematic studies of solvent effects on intrinsic rate constants of proton-transfer reactions between carbon acids and carboxylate ions as well as amines as bases in various dimethyl sulfoxide/ water mixtures have been carried out by Bernasconi et al. [769]. 

B) Ionization. Add 2 drops of Universal indicator to the amine solutions prepared in (A) and determine the approximate pH of each. Also determine the pH of 2 ml of 0.1 Af solutions of methyl, dimethyl, and trimethyl amines. Tabulate your observations. 

Dimethyl-3,7-diazabicyclo[3.3.1 Jnonane was analysed by photoelectron spectroscopy and it was shown to occur in the chair-chair conformation. MNDO calculations on the compound indicate that, in the chair-chair conformation, the N-N interaction is mainly through space.Proton affinities and ionization energies were determined, by photoelectron spectroscopy, for a series of six bicyclic amines and diamines.The radical cation of... 

The donor substituent perturbation of lone pair centers is transparently demonstrated in sulfides (Fig. 7). The parent molecule H2S exhibits for its Jt-type sulfur lone pair perpendicular to the molecular plane an ionization needle at 10.5 eV [20]. Two (H3C)3SiCH2 substituents broaden the needle considerably, indicating charge delocalization and lower its first vertical ionization potential by 2.5 eV = 241 kJ mol to 8.0 eV. In the dimethyl sulfide derivative with three RsSi substituents at the same carbon center, the total shift reaches almost 3 eV (Fig. 7), an amazing demonstration of the extreme donor power of P-trimethylsilyl substituents. Tremendous substituent perturbations are also observed at other lone-pair heterocenters such as nitrogen in amines [1, 2b], with the ionization energies IE] lowered from 10.85 eV in NH3 to 7.66 eV in N(CH2SiR3)3, a difference of 3.19 eV ... 

Five mutagenic heterocyclic aromatic amines (2-amino-3-methyl-, 2-amino-3,8-dimethyl-, 2-amino-3,4,8-trimethyI-, 2-amino-l,7 -trimethylimidazo[4,5/]-quin-oxaline, 2-amino-l-methy]-6-phenylimidazo[4,56]pyiidine) were isolated from cooked meat and separated on a C g column (A = 265 nm, atmospheric pressure chemical ionization MS capillary T = 250 C, vaporizer T = 500°C, N2 sheath gas pressure 20psi, collision voltage 13 eV). A complex 16-min 90/10 0/100 (95/5... 

According to previous reviews, ammonia and amines also retard hydro-formylation. This statement has to be corrected according to more recent work [7, 130, 131, 1042]. Contrary to the statement mentioned, the hydro-formylation reaction is accelerated by small amounts of certain amines having an ionization constant of 10 [130], as e.g. pyridine, chinoUne, picoline, lutidine, aniline, toluidine, xylididine, methyl aniline and aliphatic and aromatic amides such as N,N-dimethyl formamide, N-methyl pyrroli-done and acetanilide. If larger amounts of these amines are used with HCo(CO)4 the effect becomes smaller. Very large amounts hinder the reaction (see table 3). 

Adding a nitro group, as in the case of 4,5-dinitroveratrole, photosubstitution occurred as well, but only when using amines with a relatively high ionization potential. On the contrary, photoreduction of the nitro group took place with easily oxidized amines such as dimethyl- or triethylamine [165]. 

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