Vibrational spectra methyl groups

Fig.2 shows the infrared absorption spectrum of the tin oxide film. In order to analyze the molecular structure of the deposited film, we deposited the tin oxide film on a KBr disc with thickness of 1 mm and diameter of 13 mm. Various peaks formed by surface reaction are observed including O-H stretching mode at 3400 cm, C=C stretching mode at 1648 cm, and Sn02 vibration mode at 530 cm. The formation of sp structure with graphite-like is due to ion bombardment with hydrogen ions at the surface and plasma polymerization of methyl group with sp -CHa. 

The IR spectra of methyllithium exhibited two C—H bending vibrational modes at 1480 and 1427 cm . Their assignment was again substantiated by significant isotopic shifts to 1100 and 1043 cm in the deuterium compound (Table 1). Only one weak band was observed for ethyllithium in the C—H deformation region at 1450 cm . Moreover, a new sharp peak was detected at 1385 cm and ascribed to the C—H symmetrical bending mode of CH3. Its absence in the IR spectrum of methyllithium is a further indication that free methyl groups exist only in ethyllithium. 

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