Raman acetic acid

Ph. Traynard. Bull. soc. chim. France 1947, 316-21. Raman acetic acid dimer by carbonyl stretch, AH dimerization. 

THE STATE OF NITRIC ACID IN INERT ORGANIC SOLVENTS The absence of ions in mixtures of acetic acid and nitric acid is shown by their poor electrical conductivity and the Raman spectra of solutions in acetic acid, nitromethane, and chloroform show only the absorptions of the solvent and molecular nitric acid the bands corresponding to the nitronium and nitrate ions cannot be detected. -... 

The relative abilities of nitromethane, sulpholan, and acetic acid to support the ionisation of nitric acid to nitronium ions are closely similar to their efficiencies as solvents in nitration. Raman spectroscopy showed that for a given concentration of mixed acid (i i nitric and sulphuric acids) the concentration of nitronium ions in these three solvents varied in the order nitromethane > sulpholan > acetic acid. The concentration of mixed acid needed to permit the spectroscopic detection of nitronimn ions was 25 %, 50 % and 60 % in the three solvents, respectively (see 4.4.3). 

When acetic anhydride was in excess over nitric acid, acetyl nitrate and acetic acid were the only products. When the concentration of nitric acid was greater than 90 moles %, dinitrogen pentoxide, present as (N02+)(N0a ), was the major product and there were only small traces of acetyl nitrate. With lower concentrations of nitric acid the products were acetic acid, acetyl nitrate and dinitrogen pentoxide, the latter species being present as covalent molecules in this organic medium. A mixture of z moles of nitric acid and i mole of acetic anhydride has the same Raman spectrum as a solution of i mole of dinitrogen pentoxide in 2 moles of acetic acid. 

The use of surface-enhanced resonance Raman spectroscopy (SERRS) as an identification tool in TLC and HPLC has been investigated in detail. The chemical structures and common names of anionic dyes employed as model compounds are depicted in Fig. 3.88. RP-HPLC separations were performed in an ODS column (100 X 3 mm i.d. particla size 5 pm). The flow rate was 0.7 ml/min and dyes were detected at 500 nm. A heated nitrogen flow (200°C, 3 bar) was employed for spraying the effluent and for evaporating the solvent. Silica and alumina TLC plates were applied as deposition substrates they were moved at a speed of 2 mm/min. Solvents A and B were ammonium acetate-acetic acid buffer (pH = 4.7) containing 25 mM tributylammonium nitrate (TBAN03) and methanol, respectively. The baseline separation of anionic dyes is illustrated in Fig. 3.89. It was established that the limits of identification of the deposited dyes were 10 - 20 ng corresponding to the injected concentrations of 5 - 10 /ig/ml. It was further stated that the combined HPLC-(TLC)-SERRS technique makes possible the safe identification of anionic dyes [150],... 

Super or near-critical water is being studied to develop alternatives to environmentally hazardous organic solvents. Venardou et al. utilized Raman spectroscopy to monitor the hydrolysis of acetonitrile in near-critical water without a catalyst, and determined the rate constant, activation energy, impact of experimental parameters, and mechanism [119,120]. Widjaja et al. tracked the hydrolysis of acetic anhydride to form acetic acid in water and used BTEM to identify the pure components and their relative concentrations [121]. The advantage of this approach is that it does not use separate calibration experiments, but stiU enables identihcation of the reaction components, even minor, unknown species or interference signals, and generates relative concentration profiles. It may be possible to convert relative measurements into absolute concentrations with additional information. 

CA 34,7285(1940) (Nitration of toluene in the presence of acetic acid and nitrobenzene) b)J.Chedin S.Fene ant, MSCE 32,92-100(1945XMolecuIar composition of HNOj—AcOH mixtures studies by Raman spectroscopy) c)J.Ch6din et al, MSCE 34, 289-90(1948)(Mixtures of HNOs, AcOH, H, 0 and metallic nitrates) d)M.Kitsch C.A. 

The mixed-metal dimer [CrMo(02CMe)4] has been prepared in 30% yield by addition of [Mo(CO)6] in acetic acid, acetic anhydride and CH2C12, to a refluxing solution of [Cr2(02CMe)4(H20)2] in acetic acid and acetic anhydride.13 The yellow product is volatile and gives the expected parent ion peak in the mass spectrum. It has a Raman active v(Cr—Mo) mode at 394 cm-1 consistent with quadruple bonding. The crystal structure gives a metal-metal... 

The use of 1 1 mixed acid in sulpholan and in acetic acid was examined (table 4.1, columns (/)-( )) The variation of the concentration of nitronium ions with the concentration of mixed acids ([H2S04] [HN03], 1 1), in sulpholan (a), acetic acid (b), and nitromethane (c) are illustrated in fig. 4.1. The results for acetic acid and sulpholan were determined by Raman spectroscopy, and those for nitromethane from the infra-red spectra. 

Recently Mint and Kecki [103] examined the Raman spectra of solutions of nitric acid in anhydrous and hydrated acetic acid. They have shown that at a concentration of 2 moles HN03 per litre of CH3COOH, i.e. for the solution containing 12.6% HN03 in acetic acid, the 1304 cm 1 line, probably corresponding to the nitronium ion, N02+, can be seen. The intensity of the line increases with concentration of nitric acid. Thus we can say that the acetic acid facilitates the formation of the nitronium ion. 

Other Carboxylic Acids, The low frequency modes of acetic acid and higher carboxylic acids are not as well understood as those of formic acid, and will not be discussed in detail. Raman shifts are reported for solid benzoic acid at 190 and 400 cm (1693, 1694) and for solid tartaric acid at 52, 80, 101, 115, 144, and 164 cm (1891, 1695). Gross and Val kov conclude that the frequency of the O—H 0 vibration is near 200 cm and is unchanged either by deuterium substitution or by increase in the mass of the attached alkyl groups (830). Batuev s studies seem to be in disagreement with this conclusion (162, 163). 

Cryoscopy, Raman dimer structiures of acetic acid, pure and in various solvents. 

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