The Change in the Raman Spectra of Chloroprene and Isoprene in the Polymerization Process

1943 ◽  
Vol 16 (4) ◽  
pp. 841-847
Author(s):  
A. Gantmacher ◽  
S. Medvedev
Keyword(s):  
Raman Spectrum ◽  
Double Bond ◽  
Raman Spectra ◽  
Polymer Molecule ◽  
Polymerization Process ◽  
High Polymer ◽  
Single Bond ◽  
Double Bonds ◽  
Continuous Background ◽  
Single Bonds

Abstract 1. When chloroprene and isoprene polymerize, besides the frequency characterizing the conjugate double bond in the monomer, there appears a higher frequency corresponding to the isolated double bond in the polymer. In the polymerization process, the intensity of the frequency of the conjugate double bond decreases and the intensity of the frequency of the isolated double bond increases. Because of the increase in the number of single bonds in the polymer, the intensity of the frequency of the single bond 1005 in the polymer is considerably greater than in the monomer. 2. Even in the case of the samples with high polymer contents (greater than 50 per cent), the intensity of the frequency of the conjugate double bond is considerably greater than the intensity of the frequency of the isolated double bond. This is attributable to the fact that part of double bonds disappear during polymerization. 3. The Raman spectra of the chloroprene and isoprene polymers differ essentially from those of the monomers. To characterize the frequencies of vibration in the polymer molecule, it is essential to investigate its Raman spectrum in a medium free of the monomer. 4. The formation of highly polymeric molecules on polymerization does not result in an increase in the intensity of the continuous background in spectrograms.

Sample Stability: A Suggested Definition and Medthod of Determination

1976 ◽  
Vol 22 (12) ◽  
pp. 2045-2045
Author(s):  
Ralph E Thiers ◽  
Gaw T wu ◽  
Allen H Reed ◽  
Lawrence K Oliver
Keyword(s):  
Double Bond ◽  
Membered Ring ◽  
Double Bonds ◽  
Test Statistic ◽  
Original Magnification ◽  
Letter To The Editor ◽  
Sample Stability ◽  
Single Bonds

Abstract Volume 22 p 52, colunm 1: In two palces, "γ-GT/ml" should read "γ-GT/CC." In Figures 2 through 4 in this paper, the "X800" in the legend refers to the original magnification. p 179: In Table 2, in the —20 °C experiment, the "test statistic" of samples 5 through 18 should be more negative by 0.5 and that of sample 24 should be —7.0 rather then —5.0. These change do not affect the conclusions. p 197, column 1: In the first full paragraph, reference "(2)" should read "(21)." p 777: In Figure 1, structures B and C should not contain an endocyclic double bond (structure A is correct)-i.e., the double bonds at the tops of the seven membered ring should be single bonds. p 833: Corrections to this Table are detailed in a Letter to the Editor, p 1751, q.v. p 1324: The drawing for Figure 2 has been interchanged with the drawing in the upper half of Figure 9, p 1327. p 1427: Richard S. Schifreen should be listed as an author. p 1745, column 1: The [3H]cortisl belongs to ref. 1, and was not supplied by Diagnostic Products Corp. p 1751, column 3, first paragraph: 9.7 mg/liter should read 0.7 mg/liter.

MNDO CI study of the photoisomerization of pentadieniminium

1990 ◽  
Vol 55 (12) ◽  
pp. 2874-2879 ◽  
Author(s):  
Peter Ertl
Keyword(s):  
Schiff Base ◽  
Double Bond ◽  
Configuration Interaction ◽  
Mndo Method ◽  
Double Bonds

Photoisomerization mechanism in model retinal-like protonated Schiff base pentadieniminium was investigated by using MNDO method with configuration interaction. Isomerizations around various double bonds were studied and twisted biradical geometries in S0 and S1 states were optimized. Photoisomerization proceeds exclusively around the central double bond where the twisted S1 state is strongly stabilized and the S0-S1 gap is minimal.

The resonance Raman spectra and excitation profiles of some 4-sulfamylazobenzenes

1977 ◽  
Vol 55 (9) ◽  
pp. 1444-1453 ◽  
Author(s):  
Kamal Kumar ◽  
P. R. Carey
Keyword(s):  
Raman Spectrum ◽  
Raman Spectra ◽  
Resonance Raman ◽  
Valence Bond ◽  
Wavelength Dependence ◽  
Accurate Estimation ◽  
Intensity Changes ◽  
Stretching Vibration ◽  
Resonance Raman Spectra ◽  
Frequency Changes

The resonance Raman spectra of three pharmacologically important sulfonamides, 4-sulfamyl-4′-dimethylaminoazobenzene (1), 4-sulfamyl-4′-hydroxyazobenzene (2), and 4-sulfamyl-4′-aminoazobenzene (3), are compared with those of analogues lacking the sulfonamide group. The —SO2NH2 moiety does not directly contribute intense or moderately intense bands to the resonance Raman spectra of 1, 2, and 3. However, —SO2NH2 ionization is reflected by frequency changes in a band near 1140 cm−1 and intensity changes in the 1420 cm−1 region. The normal Raman spectrum of 2 confirms that the intensity changes reflect —SO2NH2 ionization rather than unrelated changes in vibronic coupling. The effect of —OH ionization on the resonance Raman spectrum of 2 emphasizes that caution must be exercised when relating spectral perturbations to changes in contributions from valence bond type structures. Resonance Raman excitation profiles for the 1138, 1387, and 1416 cm−1 bands of 2 show that these bands gain intensity by coupling with the electronic transitions in the 240 to 450 nm region and that, more than 1000 cm−1 to the red of λmax, the wavelength dependence can be closely reproduced by the FB type terms of Albrecht and Hutley. The excitation profile for each band shows evidence for structure in the 470 nm region, although lack of sufficient excitation wavelengths prevents accurate estimation of the spacing. Under conditions of rigorous resonance the intense Raman lines all occur in the 1400 cm−1 region, i.e. they are 'bunched' in the region known to contain the —N=N— stretching vibration.

A stereospecific synthesis of trisubstituted double bonds

1970 ◽  
Vol 23 (4) ◽  
pp. 813 ◽  
Author(s):  
AJ Birch ◽  
B McKague
Keyword(s):  
Double Bond ◽  
Stereospecific Synthesis ◽  
Considerable Proportion ◽  
Double Bonds ◽  
Steric Configuration

An aspect of the synthesis of sterically defined trisubstituted double bonds is discussed. Metal-ammonia reductions of hydropyridinium salts such as (1 ; R, R' = H or Me) result in allylic fissions, with a considerable proportion of double bond retention in its original situation and complete retention of the original steric configuration in that position.

Infrared and Raman spectra of the phosphazene high polymer [NP(O2C12H8)]n

1998 ◽  
Vol 29 (4) ◽  
pp. 327-330 ◽  
Author(s):  
Gabino A. Carriedo ◽  
Francisco J. García Alonso ◽  
Pedro A. González ◽  
José R. Menéndez
Keyword(s):  
Raman Spectra ◽  
Infrared And Raman Spectra ◽  
High Polymer

Raman Spectra of Polyisoprene Rubbers

1970 ◽  
Vol 43 (2) ◽  
pp. 313-321 ◽  
Author(s):  
S. W. Cornell ◽  
J. L. Koenig
Keyword(s):  
Double Bond ◽  
Raman Spectra ◽  
Structure Type ◽  
Peak Height ◽  
Mixed Structure ◽  
Carbon Double Bond

Abstract The Raman spectra of cis-1,4-, trans-1,4-, and 3,4-polyisoprene are presented, and the frequencies are classified by configurational structure type. The stretching frequency of the carbon-carbon double bond vibrations are used to describe structure content. Only Raman bands characteristic of total 1,4 content and total vinyl content can be observed. Tentative values of structure content determined by both peak height and peak area are presented for two mixed structure rubbers.

Chlorination of Natural Rubber in Solution with Gaseous Chlorine

1953 ◽  
Vol 26 (4) ◽  
pp. 902-911 ◽  
Author(s):  
C. S. Ramakrishnan ◽  
D. Raghunath ◽  
J. B. Pande
Keyword(s):  
Double Bond ◽  
Natural Rubber ◽  
Cyclization Reaction ◽  
Double Bonds ◽  
Chlorine Atoms ◽  
Reaction Stage ◽  
Stage 1 ◽  
Additive Reaction

Abstract The chlorination of rubber solutions by gaseous chlorine was followed by isolating the partially chlorinated products and preparing their ozonides. The ozonides were hydrolyzed, and the acids and aldehydes formed on hydrolysis were determined. By a comparison with the amounts of acids and aldehydes obtained from ozonides of unreacted rubber, the amount of residual isoprenic double bonds present was found. The loss of double bonds attending the introduction of chlorine atoms into the molecule of rubber indicates four definite stages in chlorination : (1) initial substitutive attack by chlorine, with concomitant cyclization, resulting in a loss of one double bond between two isoprenic units, (2) substitution, (3) additive reaction, and (4) essentially substitution. Chlorination of aged rubber solutions differs from the above in that the cyclization reaction (stage 1) seems to be absent.

A Novel Class of Rigid-rod Perylene Diimides and Isoindigo Semiconducting Polymers

2021 ◽  
Author(s):  
Yaping Yu ◽  
Danlei Zhu ◽  
Xiuyuan Zhu ◽  
Mahesh kumar Ravva ◽  
Jiayao Duan ◽  
...  
Keyword(s):  
Double Bond ◽  
Conjugated Polymers ◽  
Optoelectronic Properties ◽  
Semiconducting Polymers ◽  
Perylene Diimides ◽  
Rigid Rod ◽  
Single Bonds

Rigid-rod conjugated polymers contain only double-bond linkers instead of single-bonds between the monomer linkages along the backbone. These polymers exhibit exceptional optoelectronic properties and promising devices performances owing to the...

Sign in / Sign up

Export Citation Format

Share Document