Carboxylate salts, infrared spectra

With these compounds the presence of the halogen will have been detected in the tests for elements. Most acid halides undergo ready hydrolysis with water to give an acidic solution and the halide ion produced may be detected and confirmed with silver nitrate solution. The characteristic carbonyl adsorption at about 1800 cm -1 in the infrared spectrum will be apparent. Acid chlorides may be converted into esters as a confirmatory test to 1 ml of absolute ethanol in a dry test tube add 1 ml of the acid chloride dropwise (use a dropper pipette keep the mixture cool and note whether any hydrogen chloride gas is evolved). Pour into 2 ml of saturated salt solution and observe the formation of an upper layer of ester note the odour of the ester. Acid chlorides are normally characterised by direct conversion into carboxylic acid derivatives (e.g. substituted amides) or into the carboxylic acid if the latter is a solid (see Section 9.6.16, p. 1265). 

Though this is not an acid salt, and does not even involve any carboxyl groups, its structure is analogous to that of a Type A acid salt, as was predicted by Hadzi and Novak 36) from its infrared spectrum, and confirmed by X-ray work 37). 

Among the tropolone compounds found in nature are four tropolone-carboxylic acids,obtained from mold cultures.Two ofthese,stipitatonicadd(CXIV,R = COOH) and stipitatic acid (CXIV, R = H) have been obtained from Penicillium stipitatum (Bentley and Thiessen, 1963). Puberulonic add (CXV, R = COOH) and puberulic acid (CXV, R = H) were obtained from P. aurantio-virens, P. puberulum and P.johan-nioli as well as from strains of the P. cyclopium-viridicatum series (sources quoted in this paper). The infrared spectrum of the sodium salt of the anhydride of stipitatonic... 

Figure 1 presents the infrared spectra of Volo Bog humic materials in the carboxylate region as traditionally studied for the total DOC fraction smaller than 0.45 pm for dried samples obtained by using the KBr pellet (spectrum A, Figure 1) and by the diffuse-reflectance (spectrum B, Figure 1) techniques. Because hollow-fiber ultrafiltration does not rely upon chemical separation, the sample is in its natural state and is not stripped of metals or other cations. Thus, the carboxyl groups are in the form of acid salts with all major counter ions present. 

The most important metal-containing heat stabilizers in PVC can also be identified through IR-spectroscopy (see Section 8.2). Characteristic absorption bands for the salts of carboxylic acids are the bands of the ionized carboxy group in the region from 1590 to 1490 cm and from 1410 to 1370 cm Since the exact position of the absorption bands depends mainly on the metal counterions of the carboxy group, the IR-spectra provide a first identification of these metals. Tin stabilizers also show characteristic bands in these regions of the IR-spectrum. To determine the spectra, one uses pressed pellets made by finely grinding the sample material with potassium bromide. The identification of the metal becomes even more certain if an FT-IR (Fourier Transform/Infrared) instrument is available. With such an instrument, it is possible to subtract the spectrum of an additive-free... 

Fourier Transform Infrared (FTIR) spectroscopy show s a strong absorption at 1735 cm , a spectrum tyq)ical for cellulosic acid. When the sodium salt of oxidized cellulose is isolated and measured, a strong carboxylate band is seen at 1594 cm T In addition to the carboxylate band a small band (approximately 2% intensity) is uncovered at 1737 cm . This absorption may correspond to a strained ester or lactone moiety (unpublshed Zhbankov RG, 1991). 

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