Carbon-hydrogen bonds stretching

The analysis of the resulting copolymers were established by H NMR, infrared and UV—visible spectroscopies. Table 26 shows the copolymerization results by metal catalysts. The H-NMR spectra of both the monomer and the polymer are shown in Figure 33. As the polymerization proceeded, the acetylenic proton peak at around 1.96 ppm disappeared and a new vinylic proton peak appeared in the aromatic region. Also, the IR spectra of the polymer showed no absorption peaks at 3290 and 2140 cm , which are expected to be present for the acetylenic carbon—hydrogen bond stretching and carbon—carbon triple bond stretching in the monomer, respectively. [Pg.72]

Here, Do represents the equilibrium dissociation energy and or is a parameter related to the vibrational force constant. Figure 3 provides a comparison of the two potential functions used to describe the carbon-hydrogen bond stretch based on the Dauber-Osguthorpe et al. (1988) forcefield parameters. Although both represent the equilibrium... [Pg.8]

Carbon-hydrogen bond stretching of Ag symmetry is omitted because its frequency (well separated in energy from the other Ag normal modes) is not affected by changes in Fp. [Pg.782]

Kinetic isotope effect. Calculate the kie for R-H/R-T and R-D/R-T, taking for a carbon-hydrogen bond a stretching frequency of 2900 cm 1. [Pg.221]

Alkanes, alkenes, and alkynes also have characteristic C — H stretching frequencies. Carbon-hydrogen bonds involving sp3 hybrid carbon atoms generally absorb at frequencies just below (to the right of) 3000 cm-1. Those involving sp2 hybrid carbons absorb just above (to the left of) 3000 cm-1. We explain this difference by the amount of 5 character in the carbon orbital used to form the bond. The s orbital is closer to the nucleus than the p orbitals, and stronger, stiffer bonds result from orbitals with more s character. Even if an alkene s C=C absorption is weak or absent, the unsaturated C—H stretch above 3000 cm-1 reveals the presence of the double bond. [Pg.523]

To start with, we can certainly say this the carbon-hydrogen bond is stretched but not entirely broken, and the hydrogen-halogen bond has started to form but is not yet complete. This condition could be represented as... [Pg.64]

Abstraction of hydrogen by the highly reactive chlorine atom has a low act According to the postulate, then, the transition state is reached before the reaction has proceeded very far, and when the carbon-hydrogen bond is only slightly stretched. Atoms and electrons are still distributed much as they were in the reactants carbon is still nearly tetrahedral. The methyl group has developed little free-radical character. [Pg.67]

Nearly every organic compound has one or more carbon-hydrogen bonds. For this reason, the C-H stretch isn t as useful as you might think. Some guidelines are helpful ... [Pg.70]

Figure 3. Comparison of harmonic and Morse potenrials to represent the bond stretch energy of the carbon-hydrogen bond. The Morse potential is more appro-priate for modeling significant deviations from the equilibrium atom separation distanee r Do is the bond dissociation energy.

Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...