P Dimethylaminobenzoic acid

Fig. 2.4. Absorption A, fluorescence F, and degree of polarization of fluorescence P of DMABN and DMABEE (p-dimethylaminobenzoic acid ethylester) in n-hexane at room temperature, c = 5 x 10 M, and ethyl alcohol at 140 K, c = 1 x 10 4Af, respectively. Arrows indicate excitation wavenumber for measurements of P.6 Subscripts A and B refer to final and initial emission, respectively.

By implication, the H-bonding within the dimer seems to be of some importance. The accuracy of this predic-tion was tested by mixing 3,5-dinitrobenzoic acid with p-dimethylaminobenzoic acid to see if a 1 1 crystalline material formed. In this case, H-bonding between the nitro and amino groups is precluded by the methylation of the amino groups. Apparently, a stoichiometric mixed solid does form (as evidenced by an unmistakable change in color to red), although the structure has not yet been determined. 

In the aromatic series such a reaction is more often observed. For example, p- dimethylaminobenzoic acid can be nitrated to 2,4-dinitrodimethylaniline (Re-verdin [201]) ... 

Thermolysis of peroxide [29c] in benzene solution generates a chemiluminescent emission whose spectrum is identical to the fluorescence spectrum of photoexcited p-dimethylaminobenzoic acid under similar conditions. Thus the direct chemiluminescence is attributed to the formation of the singlet excited acid. The yield of directly generated excited acid is reported to be 0.24% (Dixon and Schuster, 1981). Since none of the other peroxybenzoates generate detectable direct chemiluminescence it was not possible to compare this yield to the other peroxides. However, by extrapolation it was concluded that the dimethylamino-substituted peroxide generates excited singlet products at least one thousand times more efficiently than does the peroxyacetate or any of the other peroxybenzoates examined. 

For the dimethylamino-substituted peroxyester [29c] a third type of behavior is observed. The corrected chemiluminescence intensity obtained is independent of the structure of the activator. This is just what is expected for simple indirect chemiluminescence where the activator is excited by energy transfer from some first-formed singlet state. As indicated above, the initial excited state in this system is p-dimethylaminobenzoic acid. Evidently, the electron donating p-dimethylamino-substituent renders the peroxybenzoate [29c] sufficiently difficult to reduce that the value of k2 is so small that the bimolecular path is never able to compete successfully with unimolecular decomposition. 

Other examples of ancillary ligands used to enhance analyte selectivity include amide-modified D03A (1,4,7,10-tetraazacyclododecane-l,4,7-trisacetate) complexed to Tb , which selectively binds the bidentate analytes p-dimethylaminobenzoic acid (DMABA) and SA (160-162). The binary complex of with EDTA can effectively detect SA, 4-aminosalicylic acid and 5-fluorosalicylic acid (163). [Tb(EDTA)] also has been used to detect catalysis of hydroxybenzoic acid (HBA) by hemin via formation of a ternary complex with the HBA oxidation product (164). Diaza-crown ethers have been utilized with and Eu to detect phthalate, benzoate,... 

The need to consider the effect of zwitter-ion formation applied also to Me2N. For aqueous solutions there appear to be no data relevant to obtaining a precise value of Om, but van de Graaf and colleagues have examined p-dimethylaminobenzoic acid . They obtained values of p Ti and p f2 (water, 25 °C) of 2.568 and 4.996, respectively, and calculated a value of p Ta of 4.90 for the ionization of the neutral acid. (The ratio of zwitter-ion to neutral acid is 19.4 80.6.) From this p Ta value and 4.21 for the pA"a value of benzoic acid, ap for Me2N is —0.69. 

The CRC Handbook of Chemistry and Physics [32, 33] lists a value of 6.03 for the pAia of p-dimethylaminobenzoic acid (p-DMABA). The CRC s pATa value is inconsistent with the LDM modeling which yields a value of 5.04 [21], the latter agreeing very closely with the value reported in the primary literature (pATa = 5.03) [34]. Further, a calculation based on Hammett o-constants yields a predicted p/ a of 4.85 for p-aminobenzoic acid (p-ABA) which is expected to be close to that of p-DMABA, and which corroborates that the CRC s entry for p-DMABA should be corrected to 5.03 [21]. 

When dimethyl-p-toluidine is fed to rabbits a reducing substance is excreted which probably is p-dimethylaminobenzoyl glucuronoside, for p-dimethylaminobenzoic acid can be isolated from the urine (162). If the urine is hydrolyzed with acid and distilled, o-dimethylaminophenol is produced this is probably derived from p-dimethylamino- re-hydroxybenzoic acid (164). 

Molecular rotors with a dual emission band, such as DMABN or A/,A/-dimethyl-[4-(2-pyrimidin-4-yl-vinyl)-phenyl]-amine (DMA-2,4 38, Fig. 13) [64], allow to use the ratio between LE and TICT emission to eliminate instrument- and experiment-dependent factors analogous to (10). One example is the measurement of pH with the TICT probe p-A,A-dimethylaminobenzoic acid 39 [69]. The use of such an intensity ratio requires calibration with solvent gradients, and influences of solvent polarity may cause solvatochromic shifts and adversely influence the calibration. Probes with dual emission bands often have points in their emission spectra that are independent from the solvent properties, analogous to isosbestic points in absorption spectra. Emission at these wavelengths can be used as an internal calibration reference. 

Fig. 13 Self-calibrating dyes DMA-2,4 and p-A,A-dimethylaminobenzoic acid. Compound 40 is an engineered ratiometric dye composed of a viscosity-sensitive molecular rotor and a nonviscosity-sensitive reference dye [70]...

Jiang Y (1994) pH Dependence of the twisted intramolecular charge transfer(TICT) of p-N, N-dimethylaminobenzoic acid in aqueous solution. J Photochem Photobiol A Chem 78 (3) 205-208... 

In most of these studies, hydroxyl has been the typical resident functional group, which is derivatized with appropriate acids containing chromophores suitable for exciton coupling. The ideal chromophore would have a very intense UV-visible transition, located in a convenient spectral window, and with the orientation of its electric transition moment being well-defined relative to alcohol R—OH bond. One of the most successful has been p-dimethylaminobenzoate, which has an intense (s ca 30, 000) transition in an... 

Apart from the PAR method described above, many others are based on azo reagents. Some of these methods are very sensitive for vanadium. In this group are the pyridylazophenol derivatives [44], 2-(3,5-dibromo-2-pyridylazo)-5-dimethylaminobenzoic acid (3,5-di-Br-PAMB) (e = 5.95-10 ) [45], 5-Br-PADAP (e = 5.48-10 ) [46,46a], 2-(5-chloro-2-pyridylazo)-5-dimethylaminophenol (e = 5.55-10 ) [47], A-methylanabasine-a -azo-/ -cresol (in the presence of H2O2) [48], 5-(8-quinolylazo)-2-monoethylamine-p-cresol [49], and Sulphonitrophenol K in the presence of NH2OH (e = 5.5-10 ) [50]. 

Ethyl p-dimethylaminobenzoate Benzoic acid, 4-dimethylamino-, ethyl ester (10287-53-3), 76, 276... 

Vitamin D2 3,5-dinitrobenzoate Ergocalciferol, 3,5-dinitrobenzoate (8,9) (4712-11-2) Ethyl p-dimethylaminobenzoate Benzoic acid, p-(dimethylamino)-, ethyl ester (8) Benzoic acid, 4-(dimethylamino)-, ethyl ester (9) (10287-53-3) tert-Butyl methyl ether Ether, tert-butyl methyl (8) Propane, 2-methoxy-2-methyl-(9) (1634-04-4)... 

Dimethylaminobenzoic acid p-Dimethylamino benzoic acid p-N,N-(Dimethyl-amino)benzoic acid N,N-Dimethyl-4-aminoben2oie acid NSC 16696 Solarchem 0. Esters used as ultraviolet screens. Needles mp = 242.5° Xm = 308 nm (e = 25119, EtOH) slightly soluble in EtzO, soluble in EtOH. CasChem ISP Van Dyk Inc. Upo. 

Dimethylaminobenzoic acid, ethylhexyl ester. See Octyl dimethyl PABA 2-Dlmethylaminoethanol P-Dimethylaminoethanol N,N-Dimethylamino-ethanol. See Dimethylethanolamine... 

CAS 10287-53-3 EINECS/ELINCS 233-634-3 Synonyms 4-Dimethylaminobenzoic acid, ethyl ester Ethyl-p-(dimethylamino) benzoate Classification Amine Empirical C H,5N02... 

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