Measurement of Internal Double Bonds in Polymers by Perbenzoic Acid Addition

1948 ◽  
Vol 21 (4) ◽  
pp. 821-829 ◽  
Author(s):  
Alfred Saffer ◽  
B. L. Johnson
Keyword(s):  
Double Bond ◽  
Low Ph ◽  
Side Chain ◽  
Double Bonds ◽  
Extrapolation Procedure ◽  
Perbenzoic Acid ◽  
Acid Methyl ◽  
Emulsion Polymers ◽  
Small Excess ◽  
Minimum Interference

Abstract Internal double bonds formed by 1,4-polymerization of diene monomers add perbenzoic acid more rapidly than do vinyl double bonds which are the products of the 1,2-type of addition. The extrapolation procedure proposed for determining internal double bond contents of diene polymers is based on this difference in addition rates. Oleic acid mixtures with 10-undeeylenie acid were prepared and analyzed with an accuracy of 1 per cent. However, the method is limited to systems containing 70 per cent or more internal double bonds. Minimum interference of side-chain oxidation by perbenzoic acid was attained by using a low temperature and a small excess of perbenzoic acid. Methyl-substituted emulsion polymers are characterized by high amounts of 1,4-addition. Polymerizations with alkali-metal catalysts result in products of high vinyl double-bond content. A slight preference for the 1,4-type of polymerization is favored in media of low pH. Natural rubbers are formed almost completely by 1,4-polymerization. Heat softening, modifier concentration, and extent of conversion do not influence the degree of 1,4-polymerization.

Chemistry of amidyl radicals: intramolecular reactivities of alkenyl amidyl radicals

1985 ◽  
Vol 63 (8) ◽  
pp. 2203-2210 ◽  
Author(s):  
Yuan L. Chow ◽  
Richard A. Perry
Keyword(s):  
Double Bond ◽  
Rate Constants ◽  
Side Chain ◽  
Double Bonds ◽  
Kinetic Rate ◽  
Cyclic Radical ◽  
Kinetic Rate Constants ◽  
Acyl Side Chain ◽  
Complete Reversal

Amidyl radicals possessing Δ4,5, Δ5,6, and Δ6,7 double bonds were generated from the photodecomposition of nitrosamides and chloramides and the products were identified. Dichotomies of amidyl radical reactivities were discovered and compared with published kinetic rate constants. In complete reversal to intermolecular reactivities, intramolecularly the alkenyl amidyl radicals preferentially add to the double bonds rather than abstract a C-5 hydrogen even if it is allylic. In intramolecular competition, amidyl radicals add to an acyl side chain double bond more efficiently than to an alkyl one; this is just the opposite to intramolecular H-abstraction of amidyl radicals. Taken together with the published results, it is established that, in intramolecular attacks of double bonds, amidyl radicals selectively undergo the propia-addition to generate an exo-cyclic radical rather than the longa-addition to an endo-cyclic radical: this rule should replace the old one that amidyl radicals preferentially cyclize to form five-membered rings if choices are available.

scholarly journals Epoxidation of Cardanol’s Terminal Double Bond

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2104
Author(s):  
Emre Kinaci ◽  
Erde Can ◽  
John J. La Scala ◽  
Giuseppe R. Palmese
Keyword(s):  
Double Bond ◽  
Glycidyl Ether ◽  
Tensile Modulus ◽  
Mechanical Analysis ◽  
Side Chain ◽  
Double Bonds ◽  
Fiber Reinforced Composite ◽  
Terminal Double Bond ◽  
Reinforced Composite ◽  
Polymer Properties

In this investigation, the terminal double bonds of the side chain epoxidized cardanol glycidyl ether (SCECGE) molecule were further epoxidized in the presence of Oxone® (potassium peroxomonosulfate) and fluorinated acetone. Regular methods for the double bond epoxidation are not effective on the terminal double bonds because of their reduced electronegativity with respect to internal double bonds. The terminal double bond functionality of the SCECGE was epoxidized to nearly 70%, increasing the epoxy functionality of SCECGE from 2.45 to 2.65 epoxies/molecule as measured using proton magnetic nuclear resonance (1H-NMR). This modified material—side chain epoxidized cardanol glycidyl ether with terminal epoxies (TE-SCECGE)—was thermally cured with cycloaliphatic curing agent 4-4′-methylenebis(cyclohexanamine) (PACM) at stoichiometry, and the cured polymer properties, such as glass transition temperature (Tg) and tensile modulus, were compared with SCECGE resin cured with PACM. The Tg of the material was increased from 52 to 69 °C as obtained via a dynamic mechanical analysis (DMA) while the tensile modulus of the material increased from 0.88 to 1.24 GPa as a result of terminal double bond epoxidation. In addition to highlighting the effects of dangling side groups in an epoxy network, this modest increase in Tg and modulus could be sufficient to significantly expand the potential uses of amine-cured cardanol-based epoxies for fiber reinforced composite applications.

Transformations of Steroids by Beauveria bassiana

2005 ◽  
Vol 60 (1-2) ◽  
pp. 103-108 ◽  
Author(s):  
Ewa Huszcza ◽  
Jadwiga Dmochowska-Gładysz ◽  
Agnieszka Bartmańska
Keyword(s):  
Double Bond ◽  
Beauveria Bassiana ◽  
Hydroxyl Group ◽  
Side Chain ◽  
Double Bonds ◽  
Methyl Group ◽  
Group Reduction ◽  
Group A ◽  
Acetyl Group

The course of transformations of testosterone and its derivatives, including compounds with an additional C1,C2 double bond and/or a 17α-methyl group, a 17β-acetyl group or without a 19-methyl group, by a Beauveria bassiana culture was investigated. The fungi promoted hydroxylation of these compounds at position 11α, oxidation of the 17β-hydroxyl group, reduction of the C1,C2 or C4,C5 double bonds and degradation of the progesterone side-chain, leading to testosterone. The structure of 4-ene-3-oxo-steroids had no influence on regio- and stereochemistry of hydroxylation. In a similar manner, dehydroepiandrosterone was hydroxylated by Beauveria bassiana at position 11α, however, a small amount of 7α- hydroxylation product was also formed.

A Novel Scheme for the Synthesis of 21-Acetoxypregna-1,4,9(11)-triene- 17α,21-diol-3,20-dione from 9α-Hydroxyandrostenedione

2020 ◽  
Vol 16 (5) ◽  
pp. 606-610
Author(s):  
Nguyen T. Diep ◽  
Luu D. Huy
Keyword(s):  
Double Bond ◽  
Chemical Synthesis ◽  
Economic Efficiency ◽  
Final Stage ◽  
Side Chain ◽  
Entire Process ◽  
Drug Synthesis ◽  
First Time

Background: Vietnam currently imports up to 90% of the pharmaceuticals it consumes and 100% of the steroid-based pharmaceuticals. The ability for efficient chemical synthesis of the steroids could create commercial opportunities to address this issue. Synthesis of 21-acetoxypregna-1,4,9(11)- triene-17α,21-diol-3,20-dione is considered a key intermediate in the scheme of steroidal drug synthesis. Previous synthesis attempts of such steroids (corticoids) introduce a double bond at C-1(2) in the final stage of synthesis, which delivers a poor yield and reduces the economic efficiency of the process. Objective: To study and develop a novel and effective method for the synthesis of 21-acetoxypregna- 1,4,9(11)-triene-17α,21-diol-3,20-dione. Methods: Using 9α-hydroxyandrostenedione as a substrate chemical synthesis was performed as follows: pregnane side chain construction at C-17 (acetylene method), introduction of C-1(2) double bond (using SeO2), epimerization of C-17 (via 17-ONO2 ester) and Stork’s iodination. Results: 21-acetoxypregna-1,4,9(11)-triene-17α,21-diol-3,20-dione was prepared from 9α- hydroxyandrostenedione with an improved yield compared to previous attempts. Conclusion: Here, 21-acetoxypregna-1,4,9(11)-triene-17α,21-diol-3,20-dione has been synthesized from 9α-hydroxyandrostenedione based on a novel, effective and commercially feasible scheme. The introduction of the C-1(2) double bond at an earlier stage of the synthesis has increased the economic efficiency of the entire process. For the first time, the indirect epimerization mechanism has been clarified along with the configuration of the C-17 stereo-center which has been confirmed using NOESY data.

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.

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.

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.

Critical Review of Biotransformational Studies on Steroids by Using Culture of Cunninghamella blakesleeana

2021 ◽  
Vol 18 ◽  
Author(s):  
Azizuddin ◽  
Muhammad Iqbal ◽  
Syed Ghulam Musharraf
Keyword(s):  
Double Bond ◽  
Critical Review ◽  
Structural Modification ◽  
Bond Formation ◽  
Environmentally Friendly ◽  
Side Chain ◽  
Synthetic Compounds ◽  
Efficient Approach ◽  
Cunninghamella Blakesleeana ◽  
Different Strains

: For several decades, biotransformational studies on steroidal compounds have gained a lot of attention because it is an efficient approach for the structural modification of complicated natural or synthetic compounds with high regio-, chemo- and stereoselectivity at environmentally friendly conditions. This review summarizes the use of different strains of Cunninghamella blakesleeana for the biotransformation of sixteen steroids 1-16 into a variety of transformed products. The transformed products may be important as a drug or precursor for the production of important pharmaceuticals. The types of reactions performed by C. blakesleeana include hydroxylation, epoxidation, reduction, demethylation, oxidation, glycosidation, double bond formation, side-chain degradation, isomerisation and opening of an isoxazol ring, which would be difficult to produce by traditional synthesis.

Migration of the Double Bond in the Side Chain of Sterols with Iodine.

1970 ◽  
Vol 35 (12) ◽  
pp. 4145-4148 ◽  
Author(s):  
Nobuo Ikekawa ◽  
Yasushi Honma ◽  
Naoko Morisaki ◽  
Kiyoshi Sakai
Keyword(s):  
Double Bond ◽  
Side Chain
Sign in / Sign up

Export Citation Format

Share Document