CH2COOH Group Research Articles

Synthesis and characterization of a novel macrocyclic ligand containing nine donor atoms

AbstractThe synthesis of a novel macrocyclic ligand containing nine potential coordination sites (six nitrogens and three oxygens) formed by a triazacyclododecane ring trisubstituted with CH2CH2N(CH2Ph)CH2COOH groups is reported. The protonation scheme of this ligand has been elucidated by measuring the proton NMR shifts of the various methylenic resonances upon changing the pH of the solution. This ligand affords stable metal complexes with Cd2+ ion, whose 1H‐ and 13C‐NMR spectra suggest a remarkable kinetic inertia and stereochemical rigidity.

Structures of chloralide, d-lactic acid chloralide, malic acid chloralide and citric acid chloralide

The crystal and molecular structures of chloralide ( 1), d-lactic acid chloralide ( 2), malic acid chloralide ( 3) and citric acid chloralide ( 4) have been determined by X-ray diffraction methods. Compound 1 crystallizes in the monoclinic space group, P2 1 c , a = 6.201(2), b = 17.11(2), c = 10.357(6) A ̊ , β = 95.21(4)°, Z = 4; compound 2 in the monoclinic space group P2 1, a = 7.600(4), b = 5.902(4), c = 9.743(6) A ̊ , β = 99.20(5), Z = 2; compound 3 in the monoclinic space group P2 1 c , a = 16.500(6), b = 5.819(3), c = 10.120(4) A ̊ , β = 91.41(3), Z = 4; compound 4 in the monoclinic space group P2 1 c , a = 12.041(3), b = 6.1190(10), c = 17.259(4) A ̊ , β = 101.85(2), Z = 4. The five-membered ring systems of all the compounds are slightly twisted out-of-plane, that of compound 4 being the most puckered. The CCl 3 group is trans to the second CCl 3 group in 1, to the CH 3 group in 2 and to the CH 2COOH group in 3. The two CH 2COOH groups in 4 are disposed axially with respect to the ring. Dipole moment and Kerr constant data for d-lactic acid chloralide suggest a structure in solution which is consistent with the X-ray results. The IR spectra of 2, 3 and 4 are discussed in relation to the structures of these compounds.

Synthesis and x-ray diffraction study of 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-n-acetic acid dihydroperchlorate

The dihydroperchlorate of 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-N-acetic acid (I) was obtained by the exchange reaction of the dihydrobromide with silver perchlorate. A planar structure of the ligand molecule with methyl and CH2COOH groups that deviate from the plane of the macroring was established as a result of x-ray diffraction analysis. Numerous hydrogen bonds with the participation of a carboxy group, amino nitrogen atoms, and crystallization water molecules were detected.

Wide-line NMR studies on parachlorophenoxy acetic acid

Proton magnetic resonance studies have been carried out on a polycrystalline sample of parachlorophenoxy acetic acid in the temperature range 77 to 400K. The experimental second moment (11.5 G2) agrees within the experimental error with the value calculated using the available crystal structure data, indicating that the lattice is rigid below 112K. Second moment fall, which is observed in the temperature range 112-125K, is attributed to the rapid reorientation of the CH2COOH group. This reorientation is associated with an activation energy of 7.90 kcal mol-1, which indicates that the intramolecular reorientation breaks the strong hydrogen bonds in the dimeric unit.

A nuclear magnetic resonance study of molecular motion in (2,4,5-Trichlorophenoxy)acetic acid

Proton magnetic resonance data in polycrystalline (2,4,5-trichlorophenoxy)acetic acid in the temperature range 77-400 K are reported in this communication. After a correction is made for the H-H distance in the methylene group the rigid lattice second moment (S2) coincides with the experimental value in the temperature range 77-170 K. The observed fall in S2 in the temperature range 170- 208 K is interpreted as the result of the CH2COOH group reorientation. The barrier height associated with the reorientation is found to be 8.728 kJ mol- which indicates non-cleavage of hydrogen-bonding in the dimeric unit during reorientation.

Acid-base properties of phosphine oxides in nitromethane

1. The acid-base properties of the phosphine oxides were studied by the method of potentiometric titration in nitromethane. The titration curve has two potential jumps at the points of 50% and 100% neutralization, which is due to the formation of complexes of the BHB+ type at the first stages of protonation. 2. A linear correlation was obtained between the values of pK a (CH3NO2) and the σσϕ constants of the substituents at the phosphorus atom, which permitted a calculation of the σϕ constants of the -CH2OR and -CH2COOH groups. 3. Aminomethylphosphine oxides are titrated as nitrogen bases. Substantial differences in the values of pK a (CH3+NO2) of different degrees of protonation of the molecules of these compounds are probably due to the formation of intramolecular hydrogen bonds (of the type N+-H ... N) and the inductive effect of the protonated dialkylaminomethyl group.

Photoreduction of dyes catalysed by organic and bio-molecules.

Photoreduction of methylene blue in the presence of various organic and biomolecules has been studied spectrophotometrically and potentiometrically. During the photoreduction, the emf of the system measured against calomel electrode increases and attains a plateau long before the complete reduction of the dye. This indicates that the emf developed in this system is not that of the dye/leucodye in which case the plateau of the emf value would be expected at the complete reduction of the dye. The emf has been interpreted to be mainly that of dye/dye free radical, although dye/leucodye and dye free radical/leucodye may contribute to the emf value of the system. The free radical may be formed in the system immediately after exposure to light or even in the dark at high pH. Photoreduction of methylene blue in the presence of EDTA is completely inhibited by excess magnesium ions. By using various compounds to act as electron donors in the photoreduction, it has been found that compounds having the general formula R1R2·N·CH2COOH can cause the reduction of methylene blue where R1 and R2 may be−CH2COOH or alkyl or aryl substitution. Photoreduction becomes faster with more than one−CH2COOH group in the compounds. Glycine or N-methyl glycine fails to act as a catalyst, N-phenyl glycine or N:N-diethyl glycine catalyses the photoreduction. N-phenyl- or N-ethyl amino diacetic acid causes faster photoreduction of methylene blue. Analgin causes photoreduction even in dark. The dye capri blue is not photoreduced by EDTA though there is an increase in the emf of the system on its exposure to light; but the presence of methylene blue in the system catalyses its photoreduction.