6 Two-Dimensional Correlation Spectroscopy
121
Fig. 6.7 Asynchronous 2D
correlation spectrum
constructed from NIR
spectra of n-alkanes. In red
and blue are drawn the
positive and negative peaks,
respectively. (Reprinted from
Ref. [22] with permission
from Elsevier)
bands (near 5800 and 5900 cm
−1 ) show characteristic pairs of the peaks close to
the diagonal. Owing to resolution enhancement in the asynchronous spectrum, for
the first time, the contributions from the terminal and midchain methylene groups
were observed in the spectra of liquid n-alkanes and 1-chloroalkanes. The same
authors examined the effect of chain length on MIR and NIR spectra of aliphatic
1-alcohols from methanol to 1-decanol [23]. A negative correlation between the first
overtone of the hydrogen-bonded OH (near 6300 cm
−1 ) and the second overtone of
the methylene group (near 8225 cm
−1 ) (Fig. 6.8) reveals that the intensity changes
for these two groups are in the opposite direction. Hence, an application of 2DCOS
approach provides direct evidence that the degree of self-association of liquid 1alcohols decreases with the chain length increase. It is worth to mention that the
Fig. 6.8 Synchronous
2DCOS-NIR spectra of
1-alcohols from 1-butanol to
1-decanol. In red and blue
are drawn the positive and
negative peaks, respectively
121
Fig. 6.7 Asynchronous 2D
correlation spectrum
constructed from NIR
spectra of n-alkanes. In red
and blue are drawn the
positive and negative peaks,
respectively. (Reprinted from
Ref. [22] with permission
from Elsevier)
bands (near 5800 and 5900 cm
−1 ) show characteristic pairs of the peaks close to
the diagonal. Owing to resolution enhancement in the asynchronous spectrum, for
the first time, the contributions from the terminal and midchain methylene groups
were observed in the spectra of liquid n-alkanes and 1-chloroalkanes. The same
authors examined the effect of chain length on MIR and NIR spectra of aliphatic
1-alcohols from methanol to 1-decanol [23]. A negative correlation between the first
overtone of the hydrogen-bonded OH (near 6300 cm
−1 ) and the second overtone of
the methylene group (near 8225 cm
−1 ) (Fig. 6.8) reveals that the intensity changes
for these two groups are in the opposite direction. Hence, an application of 2DCOS
approach provides direct evidence that the degree of self-association of liquid 1alcohols decreases with the chain length increase. It is worth to mention that the
Fig. 6.8 Synchronous
2DCOS-NIR spectra of
1-alcohols from 1-butanol to
1-decanol. In red and blue
are drawn the positive and
negative peaks, respectively