SEQUENTIAL SUBSTITUTION OF METHYL SIDE GROUP IN NAPTHOQUINONE AND ANTHRAQUINONE TO INVESTIGATE SENSITIVITY OF THE CARBONYL BAND

In this work, we have added methyl side group (s) on quinone and aromatic ring carbon positions of 1, 4-naphthoquinone (NQ) and on aromatic ring carbon positions of 1, 4-anthraquinone (AQ) in sequential increasing order to check sensitivity of the carbonyl band. In NQ, we observed that the aromatic substitution is more sensitive than the quinonic substitution. In fact, the sequential addition of CH3on the quinone ring C5 and C6 positions lead into the systematic lowering of the band and such lowering is in average of 5 cm-1 per methyl group. On the other hand, addition on the aromatic ring C7, C8, C9, and C10 positions resulted in mix effect. Indeed, they produce two types of carbonyl band, which are couple and uncouple. For further exploration of the sensitivity of the carbonyl band, we put single or two methyl group (s) on C7, C8, C9, and C10 carbon positions producing four or six NQ model molecules. We concluded that the carbonyl intense bands are more sensitive, split up, to the aromatic ring methyl substitution at C7 or C10 position. Furthermore, in AQ couple mode of C=O vibration was observed and no splitting of the band was seen on sequential CH3 addition.Journal of Institute of Science and TechnologyVolume 22, Issue 1, July 2017, Page: 137-146

Observation of Intermolecular Hydrogen Bonding Interactions in Biosynthesized and Biodegradable Poly [(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate] in Chloroform and 1,1,1,3,3,3-Hexafluoro-2-propanol (HFIP)

In this work, we describe polymer–solvent interactions in biosynthesized and biodegradable poly[(R)-3-hydroxybutyrate- co-(R)-3-hydroxyhexanoate] (PHBHx) and the atactic homopolymer, poly(3-hydroxybutyrate) (a-PHB), which were studied both as neat polymers and in solutions of chloroform and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP). Specifically, infrared frequency shifts of the carbonyl band were observed in semi-crystalline PHBHx, but not in a-PHB, because it cannot form the helical conformation required for crystallization. The carbonyl band of PHBHx exhibited the high frequency associated with amorphous structure in chloroform and the lower frequency traditionally attributed to the helical crystalline structure in HFIP. The same results were obtained for a-PHB, demonstrating that the helical structure is not required for a lower frequency carbonyl-stretching mode. It is proposed that the band shift is due to hydrogen bonding between the carbonyl and hydroxyl hydrogen in HFIP. Therefore, the carbonyl frequency observed upon crystallization is most likely due to hydrogen bonding between the carbonyl and methyl hydrogen of the neighboring polymer chain in the crystal lattice as previously suggested.

Synthesis of Gold Nanoparticles Dispersed in Palm Oil Using Laser Ablation Technique

Gold nanoparticles have more applications in biology, medicine, and industry. In this study, gold nanoparticles were synthesized in pure palm oil using laser ablation technique. Gold nanoparticles were fabricated in different temperature, and the effect of the temperature on the particle size was investigated. Consequently, the tail of the carbonyl band of fatty acids was capped gold nanoparticles, and spherically shaped gold nanoparticles with size range of 8.92 to 19.73 nm were formed in palm oil. The temperature caused the agglomeration of nanoparticles while the particle size increased with an increase in the temperature.

Effect of specificity on ligand conformation in acyl-chymotrypsins

I.r. difference spectroscopy combined with 13C and 18O double-isotope substitution was used to examine the ester acyl carbonyl stretching vibration of hydrocinnamoyl-chymotrypsin. A single acyl carbonyl stretching band was observed at 1731 cm-1. This contrasts with previous i.r. and resonance Raman spectroscopic studies of a number of trans-3-arylacryloyl-chymotrypsins which showed two acyl carbonyl stretching bands in the region of 1700 cm-1, which were proposed to represent productive and non-productive conformations of the acyl-enzyme. The single acyl carbonyl band for hydrocinnamoyl-chymotrypsin suggests only a single conformation, and the comparatively high frequency of this band implies little or no hydrogen-bonding to this carbonyl group. Enzymic hydrogen-bonding to the acyl carbonyl is believed to give bond polarization and thereby catalytic-rate acceleration. Thus, in view of the apparent lack of such hydrogen-bonding in hydrocinnamoyl-chymotrypsin, it should be the case that this acyl-chymotrypsin is less specific than trans-3-arylacryloyl-chymotrypsins, whereas the opposite is true. It is therefore proposed that there may be a productive acyl carbonyl population of lower stretching frequency for hydrocinnamoyl-chymotrypsin, but that this is too small to be discerned because of either a relatively high deacylation rate or an unfavourable conformational equilibrium. The single acyl carbonyl band for hydrocinnamoyl-chymotrypsin is significantly broader than those for trans-3-arylacryloyl-chymotrypsins, indicating that this group is more conformationally mobile and dispersed in the former. This can be correlated with the absence of acyl carbonyl hydrogen-bonding in hydrocinnamoyl-chymotrypsin, and with the much greater flexibility of the saturated hydrocinnamoyl group than unsaturated trans-3-arylacryloyl. This flexibility is presumably the reason why hydrocinnamoyl-chymotrypsin is more specific than trans-3-arylacryloyl-chymotrypsins. Resonance Raman spectroscopy is limited to the non-specific trans-3-arylacryloyl-chymotrypsins because of its chromophoric requirement, whereas i.r. may be used to examine non-chromophoric more specific acyl-enzymes such as hydrocinnamoyl-chymotrypsin. The results presented in this paper suggest that trans-3-arylacryloyl-chymotrypsins are atypical.

L'azote n'est pas le site basique des amides encombrés

The shift of the carbonyl band of the iodine complexes with the hindered amides i-PrCON(C6H11)2, t-BuCON(C6H11)2, and t-BuCON(i-Pr2) shows that the iodine interacts with the oxygen atom of the carbonyl group. Hydrogen bond donors, such as p-FC6H4OH, CHCl3, or CHBr3, also interact with the oxygen atom of the carbonyl group. The only differences between these hindered amides and unhindered amides like MeCONMe2 are the lower complexation constants (15 L mol−1 for MeCONMe2–I2 vs. 3 L mol−1 for t-BuCON(i-Pr2) and a lower stoichiometry of complexation (for example, a mixture of 1:1 and 1:2 complexes is obtained with t-BuCON(C6H11)2 while MeCONMe2 forms mainly 1:2 complexes).

Microscopic FT-IR Studies of Epoxy Adhesive Films on Chemically Treated Aluminum

Microscopic reflection-absorption FT-IR spectra were obtained on epoxy adhesive films on treated and untreated aluminum. Compositional differences were observed across the interphase. The epoxy on the untreated Al showed a large amount of the curing agent and its salt form near the surface relative to the bulk. In the case of the anodized Al surfaces, less curing agent was found, along with a relatively large amount of unreacted epoxy. An additional carbonyl band was found in the untreated Al sample, probably due to reaction of the curing agent with surface water. These results indicate that the surfaces are inducing selective adsorption, leading to differences in the composition of the cured adhesive bond.

Infrared spectra of 2α-substituted 3-oxotriterpenoids and conformation of ring A

Infrared spectra of triterpenoid 19β,28-epoxy-18α-oleanane 3-ketones I - VI in the region of carbonyl stretching frequencies have been studied. Comparison of the spectra of crystals with those of solutions in various solvents, together with comparison of fundamental C=O frequencies with their first overtone leads to the conclusion that the doublet character of the carbonyl band in the solution of ketones I - IV with polar substituent in position 2α is caused by the chair-boat equilibrium of the ring A.

A Spectroscopic Study of Pivalophenone, 2-Pivaloylfuran, 2-Pivaloylthiophen and 2-Pivaloylselenophen, and their Sulphur Analogues

Infrared, ultraviolet, 1H and 13C nuclear magnetic resonance spectra were recorded for the title compounds. The infrared carbonyl-band frequencies and intensities, and the H5 chemical shifts, of planar acetophenone, 2-acetylfuran, 2-acetylthiophen and 2-acetylselenophen indicate the order Phenyl < 2-Furyl < 2-Thienyl < 2-Selenyl for Aryl-carbonyl conjugation. Ultraviolet K-band absorption coefficients and carbon-13 chemical shifts provide an estimate of the twisting angle in the pivaloyl derivatives.