The peaks observed on the functionalized CNTs at 1634 and 1460 [cm.sup.-1] can be attributed to the carboxylate anion
stretching mode of the carboxylic groups formed due to the oxidation of surface carbon atoms by nitric acid.
This characteristic band is due to asymmetric stretching in carboxylate anion
that is reconfirmed by another peak at 1422 cm 1 which is related to the symmetric stretching mode of the carboxylate anion
A displacement is also observed in the asymmetric vibration band of the carboxylate anion
from 1600.1 to 1581.8 [cm.sup.-1] with a parallel shift to frequencies (1310 to 1242.2 [cm.sup.-1] and 1098.3 to 1094.7 [cm.sup.-1]) for C-O stretch.
The characteristic band at 1558 [cm.sup.-1] is due to C=O asymmetric stretching in carboxylate anion
that is reconfirmed by another peak at 1411 [cm.sup.-1] which is related to the symmetric stretching mode of the carboxylate groups .
Selected ion monitoring was performed to monitor the carboxylate anion
(M-181; loss of [sup.*.C][H.sub.2][C.sub.6][F.sub.5]) at ions m/z 569 and 573 for [F.sub.2]-iPs and the internal standard, respectively.
This has led to an important new concept in solid state chemistry, that of the ionic chiral auxiliary, whereby the enantioselectivity of a chemical reaction of an organic ion (for example, a carboxylate anion
) in the crystalline state can be controlled by the presence of an optically active counterion (e.g., an optically active ammonium ion).
The band at 1588 [cm.sup.-1] is attributed to C=O asymmetric stretching in carboxylate anion
, and another sharp peak at 1409 [cm.sup.-1] is related to the symmetric stretching mode of carboxylate anion
The formation of carboxylate anion
was done by dissolving the acid in NaOH solution and the anion was intercalated between inorganic lamella of the MgAl-LDHs as evidence from powder X-ray and FT-IR studies and will be discussed later.
The intense characteristic band at 1573 cm-1 is due to C=O asymmetric stretching in carboxylate anion
that is reconfirmed by another sharp peak at 1416 cm-1 which is related to the symmetric stretching mode of the carboxylate anion
Upon deprotonation, the negative charge is probably localized either on the carboxylic acid group (as a carboxylate anion
) or on the phenolic group (to form a phenolate anion).
The catalyst 2MI initiates the ring-opening reaction of the epoxy group of pDGEBA to form an oxygen anion, which subsequently picks up hydrogen from carboxyl in DACA to yield a carboxylate anion
[reaction (1) of Scheme 2].
The spectra of [SH.sub.6:4] and [SH.sub.8:4] indicated appearance of a new absorbance band at 1568 [cm.sup.-1], which was assigned to the asymmetric stretching of the carboxylate anion
, indicating partial hydrolysis of the amide group into a carboxylate group and production of ammonia.