Nitrile group absorption

Notably, starting and intermediate nitriles used in the synthesis of 2-amino-3-cyanopyrans show moderate to weak nitrile group absorption at 2260-2220 cm, the nitrile band is very characteristic. 

Replacing the nitrile group by a benzothiazole produces an important subclass of fluorescent compounds represented by thioflavin T (25, Fig. 10). It is not clear if this compound undergoes deactivation via intramolecular rotation that would meet the criterion for a molecular rotor. The steady-state absorption and emission properties of thioflavin T has been attributed to micelle formation [53, 54], dimer and excimer formation [55, 56], and deactivation through intramolecular rotation [57]. 

As particular types of vibration always occur at a similar wavenumber, it is possible to build up a table of characteristic absorptions. Such a table is given on p. 14 of the SQA Data Booklet. If you examine this table, you will see, for example, that an absorption in the wavenumber range 2260-2215 cm is indicative of a nitrile group and is due to stretching of the C=N bond. So, given the infrared spectrum of an unknown organic compound and a table of characteristic absorptions, it should be possible to identify the functional groups present in the compound. In most cases, however, more information is required to determine the full structure. 

A compound that includes an aminopyrimidine ring as well as the quaternary salt present in thiamine shows preferential inhibition of absorption of that co-factor by coccidia parasites over uptake by vertebrates. The compound is thus used in poultry where coccidiosis is an economically important disease. Condensation of ethoxymethylenemalononitrile (42-1) with the amidine (42-2) leads to the aminopyrimidine (42-4), probably via the intermediate addition-elimination intermediate (42-3). The nitrile group is then reduced to the methylamino derivative (42-5) by means of hthium aluminum hydride. Exhaustive methylation, for example by reaction with formaldehyde and formic acid, followed by methyl iodide leads to the quaternary methiodide (42-6). The quaternary salt is then displaced by bromine, and the resulting benzyhc-like cylic halide (42-7) is displaced by 2-picoline (42-8). There is thus obtained amprolium (42-9) [43]. 

A first indication of the composition of the present sample was obtained from the contour plot in Fig. 32. Component 3 shows typical absorption peaks of a phenyl benzotriazole and can be identified as a UV stabilizer of the Tinuvin type. Component 2 exhibits absorption peaks which are characteristic for nitrile groups (2237 cm x) and styrene units (760,699 cm-1), while component 1 shows a strong ester carbonyl peak around 1740 cm"1 and peaks of styrene units. In agreement with the peak pattern of literature spectra, component 2 can be identified as a styrene-acrylonitrile copolymer. Component 1 is either a mixture of... 

Hie properties of SAN are significantly altered by water absorption (16). Hie equilibrium water content increases with temperature while the time required decreases. A large decrease in T can result. Strong aqueous bases can degrade SAN by hydrolysis of the nitrile groups (17). 

Acrylonitrile and related compounds displace all the carbonyl groups from nickel carbonyl to form [(RCH CHCN)2Ni], in which the nitrile bonds through the olefinic double bond 222, 418). The bis(acrylonitrile) complex catalyzes many reactions, including the conversion of acrylonitrile and acetylene to heptatrienenitrile and the polymerization of acetylene to cyclooctatetraene 418). Cobalt carbonyl gave a brown-red amorphous material with acrylonitrile, which had i cn absorptions typical of uncoordinated nitrile groups, but interestingly, the presence of C=N groups was also indicated 419). In acidic methanol, cobalt carbonyl converts a,j8-unsaturated nitriles to saturated aldehydes 459). 

The results obtained with other a-halonitriles are indicated in Table VII. With the exception of chlorodiphenylacetonitrile, PMR spectra of the resulting complexes indicated attachment of the cobalt atom alpha to the nitrile group. In the case of chlorodiphenylacetonitrile (in 25 ml. benzene), the benzene layer was separated from the yellow-aqueous layer after 1 hour reaction time. Adding ethanol to the benzene solution yielded tetraphenylsuccinonitrile, m.p. 203-4°C. (acetic acid) (205°C. reported) (49), The aqueous layer was worked up in the usual manner to obtain a white solid, exhibiting a single cyanide absorption band at 2130 cm." and a carbonyl absorption at 1575 cm.. The PMR spectrum showed aromatic and aliphatic protons in the ratio 10 1. 

We calculate an index of hydrogen deficiency of three. A quick glance at the infrared spectrum reveals the source of unsaturation implied by an index of three a nitrile group at 2260 cm (index = two) and a carbonyl group at 1747 cm (index = one). The frequency of the carbonyl absorption indicates an unconjugated ester. The appearance of several strong C—O bands near 1200 cm confirms the presence of an ester functional group. We can rule out a CM2 bond because they usually absorb at a lower value (2150 cm ) and have a weaker intensity than compounds that contain C=N. 

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