Infrared spectra of alcohols

The infrared spectra of alcohols change markedly with increasing concentration. For example, at very low concentration, the infrared spectrum of te/t-butyl alcohol in carbon tetrachloride contains a single sharp band at approximately 3600 cm corresponding to the OH stretching motion. As the alcohol s concentration increases (by adding more alcohol to the sample), a second broad OH stretch band grows in at approximately 3400 cm and eventually replaces the other band. 

Infrared We discussed the most characteristic features of the infrared spectra of alcohols earlier (Section 13.19). The O—H stretching vibration is especially easy to identify, appearing in the 3200-3650 cm region. As the infrared spectrum of cyclohexa-nol, presented in Figure 15.4, demonstrates, this peak is seen as a broad absorption of moderate intensity. The C—O bond stretching of alcohols gives rise to a moderate to... 

A. V. Stuart, Specific Influence of Solvents on the Infrared Spectra of Alcohols, J. Chem. Phys. 21, 1115, 1953. 

Iron(II) complexes are often included in studies when complexes are prepared from a large number of different metal ions. 2-formylpyridine thiosemicarbazone, 5, forms brown [Fe(5)2A2] (A = Cl, Br) when prepared in ethanol and [Fe(5-H)2] from aqueous alcohol solution [156], All of these complexes are diamagnetic. The resonance Raman and infrared spectra of [Fe(5-H)2] were examined in detail [130] and coordination occurs via the pyridyl nitrogen, azomethine nitrogen and thiol sulfur. There is appreciable d-d sulfur-to-iron(II) Jt-bonding. Solution studies of iron(II) complexes of some 5-substituted-2-formylpyridine thiosemicarbazones have been reported [157], but no solids... 

The infrared spectra of cimines show one or two N-H stretches in the 3500-3200 cm region. Primary cimines usually have two bands, while secondary amines usually have one band. Obviously, since there are no N-H bonds, tertiary amines have no N-H stretch. The bands are small and sharp in compcirison the corresponding alcohol peaks. 

Reduction of an alcoholic suspension of m-[PtCI2(PPh3)2] with hydrazine hydrate in the presence of an acetylene (ac) gives stable complexes of the type [Pt(PPh3)2(ac)] (41). The infrared spectra of the complexes indicate that the C C bond of the acetylene has been reduced almost to a C C bond, and preliminary X-ray studies (173) support the planar structure (XXXIX) in which the bonding is similar to that in the corresponding olefin complexes... 

Figure 6. Infrared spectra of dried films of (a) butyl alcohol-extracted membrane protein and (b) beef erythrocyte membranes, taken on CaF2 plates. No shoulder characteristic of the /3 conformation occurs at 1630 cmr1...

Perhaps you are curious as to why absorptions are observed in the infrared spectrum of alcohols that correspond both to free and bydrogen-borided hydroxyl groups, whereas only one OH resonance is observed in their proton nmr spectra. The explanation is that the lifetime of any molecule in either the free or the associated state is long enough to be detected by infrared absorption but much too short to be detected by nmr. Consequendy, in the nmr one sees only the average OH resonance of the nonhydrogen-bonded and hydrogen-bonded species present. The situation here is very much like that observed for conformational equilibration (Section 9-IOC). 

Infrared spectra of high polymers. V. Polyvinyl alcohol. T. Polymer... 

Gibberellin A5 (C H Os) has a melting point of 260-61° and forms a methyl ester (m.p. 190-91°). The infrared spectra of Nujol mulls of the acid and ester (see Table II) show the presence of alcoholic hydroxyl, hydroxyl of carboxylic acid, unconjugated five-ring lactone, carboxyl (or ester) carbonyl, exocyclic methylene group, and a cis-disubstituted double bond. Catalytic hydrogenation of the methyl ester confirmed the presence of two double bonds. 

It can be assumed that two separate networks with no covalent bonds between the UPR and the cyanate-based triazine network are formed. The possible addition of terminal hydroxyls from the unsaturated polyester to the —C = N bonds in BPA/DC is rather improbable as the addition of alcohols to cyanates, leading to iminocarbonate derivatives (Scheme 8), only occurs in the presence of strong alkali catalysts [134], The cyanate cyclotrimerization has been evidenced from disappearance of the 2230 and 2270 cm-1 and the appearance of 1370 and 1560 cm-1 absorption bands in the infrared spectra of the crosslinked IPN. 

The infrared spectra of a number of hydroxyalkylmetallocenes have been interpreted in terms of hydrogen bonding involving the metal atom. The best example is provided by the epimeric alcohols (XVI and XVII), which exhibit absorption at 3610 and 3561 cm. , respectively, in dilute carbon disulfide solution 23, 24, 59), The low frequency band which, with the absorption near 3600 cm. appears as well in the spectra of acyclic a- and jS-hydroxyalkylferrocenes, has been assigned to the metal-bound hydrogen bond 23, 24, 59, 61),... 

Figure 16.1. Infrared spectra of (a) 5cc-butyl alcohol and (b) bens yl alcohol.

The use of trichloroacetyl isocyanate to generate carbamates in situ can be used to identify methyl groups adjacent to a tertiary alcohol (downfield shift of 0.29—0.44 p.p.m.) and to assign the geometry of double bonds in allylic alcohols. Similarities in the n.m.r. and infrared spectra of monoterpenoids may be valuable in identifying new sesquiterpenoid analogues. ... 

Infrared The infrared spectra of phenols combine features of those of alcohols and aromatic compounds. Hydroxyl absorbances resulting from O—H stretching are found in the 3600-cm region, and the peak due to C—O stretching appears around 1200-1250 cm These features can be seen in the infrared spectrum of p-cresol, shown in Figure 24.3. 

The infrared spectra of n-butyl alcohol in carbon tetrachloride (no hydrogen bonding) and in diethyl ether. The hydrogen bonding with the fatter solvent leads to a shift to lower frequencies and an intensification of the band. 

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