Rubber. XVIII. Various Ozonides of Rubber and the Problem of the Existence of the Primary Ozonides of Harries

1938 ◽  
Vol 11 (1) ◽  
pp. 7-31
Author(s):  
Rudolf Pummerer ◽  
Hermann Richtzenhain
Keyword(s):  
Carbon Chain ◽  
Mesityl Oxide ◽  
Addition Reactions ◽  
Reaction Products ◽  
Primary Reaction ◽  
Carbon Chains ◽  
Fundamental Objection ◽  
Great Stress ◽  
Valuable Service ◽  
General Method

Abstract A permanently valuable service was rendered by Harries when he introduced the ozone cleavage of unsaturated compounds as a general method of investigation in organic chemistry. By analogy with other addition reactions of double bonded carbon atoms he derived the formula (a) for the ozonides which are first formed, but to support the existence of which he was able to obtain only scant experimental data. Harries relied above all on two observations, first, that mesityl oxide ozonide reverts to mesityl oxide when heated by itself, and, secondly, that fumaric acid is supposed to combine loosely with ozone and then readily split off again. Both of these suppositions have remained undisputed up to the present time. Harries reported that it was not possible, with any of a wide variety of reducing agents, to reduce the ozonides to the original compounds or to 1,2-glycols, as would be expected from their structure. Staudinger has laid great stress on this fundamental objection, and he considers that most ozonides have an isoözinide formula, as shown by formula (b) above, in which the carbon chain is already ruptured, so that by reduction only the usual types of cleavage products rather than glycols with intact carbon chains can be formed, as has been found experimentally. Staudinger assumed that the primary reaction products of treatment with ozone are molozonides containing the group:

Various Ozonides of Rubber and the General Question of the Existence of Primary Ozonides

1937 ◽  
Vol 10 (1) ◽  
pp. 114-119
Author(s):  
R. Pummerer
Keyword(s):  
Organic Chemistry ◽  
Experimental Data ◽  
Double Bond ◽  
Carbon Chain ◽  
Mesityl Oxide ◽  
General Question ◽  
Addition Reactions ◽  
Reaction Products ◽  
Important Method ◽  
General Acceptance

Abstract Harries was the first to make use of ozone cleavage at the carbon double bond of unsaturated compounds as an important method of research in organic chemistry. However, the formula (see PDF for diagram) of Harries, which is founded on its analogy with the products of other addition reactions, rests on scanty experimental data. One of the chief arguments against the formula is the absence of glycols as reaction products by the action of the most varied types of reducing agents. This latter fact, in conjunction with certain polymerization phenomena, led Staudinger to propose an isoozonide type of formula, in which the carbon chain has been opened, thus (see PDF for diagram) According to Staudinger, these isoozonides are formed very readily by transposition from primary or molozonides, and they are stable compounds. On the contrary, some molozonides are stabilized by polymerization. The constitution of butylene ozonide was proved synthetically by Rieche and Meister to be that of an isoozonide, and today the isoozonide formula has received general acceptance. In spite of these facts, some of the results of Harries, on which he based his original ozonide formula, remain unchallenged; for instance, the fact that when heated the ozonide of mesityl oxide reverts to mesityl oxide, and the fact that fumaric acid forms with ozone a loose compound from which ozone is liberated easily. In view of this, it appeared as if the Harries formula would really turn out to be the correct one, and that stable molozonides should exist.

Carbon Chain Growth by Sequential Reactions of CO and CO2 with a Transition Metal Carbonyl Complex

2018 ◽  
Author(s):  
Richard Kong ◽  
Mark Crimmin
Keyword(s):  
Transition Metal ◽  
Metal Carbonyl ◽  
Carbon Chain ◽  
Chain Growth ◽  
Carbonyl Complex ◽  
Fischer Tropsch ◽  
Carbon Chains ◽  
Sequential Coupling ◽  
Energy Economy ◽  
Sequential Reactions

<i>The formation of carbon chains by the coupling of COx (X = 1 or 2) units on transition metals is a fundamental step relevant to Fischer-Tropsch catalysis. Fischer-Tropsch catalysis produces energy dense liquid hydrocarbons from synthesis gas (CO and H2) and has been a mainstay of the energy economy since its discovery nearly a century ago. Despite detailed studies aimed at elucidating the steps of catalysis, experimental evidence for chain growth (Cn to Cn+1 ; n > 2) from the reaction of CO with metal complexes is unprecedented. In this paper, we show that carbon chains can be grown from sequential reactions of CO or CO2 with a transition metal carbonyl complex. By exploiting the cooperative effect of transition and main group metals, we document the first example of chain propagation from sequential coupling of CO units (C1 to C3 to C4), along with the first example of incorporation of CO2 into the growing carbon chain.</i><br>

scholarly journals Impact of Chitosan-Genipin Films on Volatile Profile of Wine along Storage

2021 ◽  
Vol 11 (14) ◽  
pp. 6294
Author(s):  
M. Angélica Rocha ◽  
Manuel Coimbra ◽  
Sílvia Rocha ◽  
Cláudia Nunes
Keyword(s):  
Volatile Compounds ◽  
Carbon Chain ◽  
White Wine ◽  
Maillard Reaction Products ◽  
Red Wines ◽  
Reaction Products ◽  
Ethyl Hexanoate ◽  
Organoleptic Characteristics ◽  
Strecker Aldehydes ◽  
Key Odorants

Chitosan-genipin films have been proposed for preservation of white wine, maintaining their varietal key odorants and organoleptic characteristics of sulfur dioxide treated wines. Nevertheless, these wines showed aroma notes that slightly distinguish them. It is possible that during the contact of films with wine for at least 2 months, after fermentation and prior to bottling, interactions or chemical reactions are promoted. In this work, wine model solutions with volatile compounds in contact with chitosan-genipin films were performed to evaluate their evolution along time. To complement these analyses, the volatile compounds of white and red wines kept in contact with chitosan-genipin films during 2 and 8 months were also studied. The results obtained allowed us to conclude that the contact of chitosan-genipin films with both white and red wines tend to retain long carbon chain volatile compounds, such as ethyl hexanoate and octan-3-one. It also promoted the formation of Maillard reaction products, such as furfural by dehydration of pentoses and Strecker aldehydes, such as 3-methylbutanal and phenylacetaldehyde, by degradation of amino acids. This study reveals that the use of chitosan-genipin films for wine preservation is also able to promote the formation of compounds that can modulate the wines aroma, maintaining the varietal notes.

The Use of N-alkanes for Estimating Intake and Passage Rate in Horses

1996 ◽  
Vol 1996 ◽  
pp. 98-98
Author(s):  
B M L McLean ◽  
R W Mayes ◽  
F D DeB Hovell
Keyword(s):  
Recent Work ◽  
Chain Length ◽  
Carbon Chain ◽  
Carbon Chain Length ◽  
Passage Rate ◽  
Forage Crops ◽  
Carbon Chains ◽  
Naturally Occurring ◽  
Chain Lengths ◽  
Long Chain

Alkanes occur naturally in all plants, although forage crops tend to have higher alkane contents than cereals. N-alkanes have odd-numbered carbon chains. They are ideal for use as markers in feed trials, because, they are inert, indigestible and naturally occurring, and can be recovered in animal faeces. Synthetic alkanes (even-numbered carbon chains) are available commercially and can also used as external markers. Dove and Mayes (1991) cite evidence indicating that faecal recovery of alkanes in ruminants increases with increasing carbon-chain length. Thus the alkane “pairs” (e.g. C35 & C36, and C32 & C33) are used in calculating intake and digestibility because they are long chain and adjacent to each other. However, recent work by Cuddeford and Mayes (unpublished) has found that in horses the faecal recovery rates are similar regardless of chain lengths.

The Effect of Trialkyl Phosphites and Other Oil Additives on the Boundary Lubrication of Ceramics: Friction of Silicon-Based Ceramics

1992 ◽  
Vol 114 (4) ◽  
pp. 653-658 ◽  
Author(s):  
Kei Demizu ◽  
Hiroyuki Ishigaki ◽  
Hideo Kakutani ◽  
Fukuzo Kobayashi
Keyword(s):  
Silicon Nitride ◽  
Boundary Lubrication ◽  
Carbon Chain ◽  
Hertzian Contact ◽  
Carbon Chain Length ◽  
Friction Coefficients ◽  
Oil Additives ◽  
Carbon Chains ◽  
Trialkyl Phosphites ◽  
Silicon Based

In order to examine the fundamental boundary lubrication properties of ceramics, reciprocating friction experiments of silicon based ceramics such as silicon carbide and silicon nitride were conducted with trialkyl phosphites and other oil additives. When ceramics were slid against ceramics, trialkyl phosphites with long carbon chains reduced the friction of silicon nitride markedly; the friction coefficients decreased with an increase in the carbon chain length. Other oil additives, however, did not greatly affect the friction. When ceramics were slid against metals, additives containing chlorine or sulfur increased friction of certain sliding couples. On the other hand, a trialkyl phosphite reduced friction and the friction coefficients increased with an increase in the maximum Hertzian contact pressure.

Aprotic Conjugate Addition Reactions of Lithiated Allylic Sulfoxides With Acyclic Enones; a Breakdown of the trans-Decalyl Transition State

1989 ◽  
Vol 42 (10) ◽  
pp. 1785 ◽  
Author(s):  
RK Haynes ◽  
AG Katsifis ◽  
LM King ◽  
SC Vonwiller
Keyword(s):  
Transition State ◽  
Conjugate Addition ◽  
Vinyl Ketone ◽  
Methyl Vinyl Ketone ◽  
Mesityl Oxide ◽  
Addition Reactions ◽  
State Characteristic ◽  
Methyl Vinyl ◽  
Cyclic Enones ◽  
Carbonyl Addition

The reactions of lithiated 1-(t-butylsulfinyl)prop-2-ene, 1-(t-butylsulfinyl)-3-methylbut-2-ene, 1-(t-butylsulfinyl)but-2-ene, 1-(phenylsulfinyl)but-2-ene and 2-methyl-1-(phenylsu1finyl)prop- 2-ene with methyl vinyl ketone, mesityl oxide and crotonaldehyde give largely carbonyl addition products arising from reaction through C1 or C3 of the allyl system. In the case of methyl crotonate, conjugate addition through C3 is observed. The initially formed diastereomers of the C1 adducts, allylic sulfoxides, are configurationally unstable. Only the lithiated 1-(t-butylsulfinyl)-3-methylbut-2-ene undergoes conjugate addition with methyl vinyl ketone to give an (E)-vinyl sulfoxide whose formation may involve the trans-decalyl transition state characteristic of the reactions of lithiated allylic sulfoxides with cyclic enones.

scholarly journals Structural basis for the broad substrate specificity of two acyl-CoA dehydrogenases FadE5 from mycobacteria

2020 ◽  
Vol 117 (28) ◽  
pp. 16324-16332
Author(s):  
Xiaobo Chen ◽  
Jiayue Chen ◽  
Bing Yan ◽  
Wei Zhang ◽  
Luke W. Guddat ◽  
...  
Keyword(s):  
Substrate Specificity ◽  
Mycobacterium Smegmatis ◽  
Hydrophobic Interactions ◽  
Carbon Chain ◽  
Structural Basis ◽  
Broad Substrate Specificity ◽  
Carbon Chains ◽  
Binding Cavity ◽  
Π Stacking Interaction ◽  
Acyl Coa Dehydrogenases

FadE, an acyl-CoA dehydrogenase, introduces unsaturation to carbon chains in lipid metabolism pathways. Here, we report that FadE5 fromMycobacterium tuberculosis(MtbFadE5) andMycobacterium smegmatis(MsFadE5) play roles in drug resistance and exhibit broad specificity for linear acyl-CoA substrates but have a preference for those with long carbon chains. Here, the structures ofMsFadE5 andMtbFadE5, in the presence and absence of substrates, have been determined. These reveal the molecular basis for the broad substrate specificity of these enzymes. FadE5 interacts with the CoA region of the substrate through a large number of hydrogen bonds and an unusual π–π stacking interaction, allowing these enzymes to accept both short- and long-chain substrates. Residues in the substrate binding cavity reorient their side chains to accommodate substrates of various lengths. Longer carbon-chain substrates make more numerous hydrophobic interactions with the enzyme compared with the shorter-chain substrates, resulting in a preference for this type of substrate.

The gaseous oxidation of 2-methyl-but-2-ene. I. Kinetic and analytical studies

1961 ◽  
Vol 262 (1310) ◽  
pp. 318-327 ◽  
Keyword(s):  
Double Bond ◽  
Methyl Alcohol ◽  
Initial Pressure ◽  
Pressure Increase ◽  
Reaction Products ◽  
Initial Attack ◽  
Primary Reaction ◽  
Slow Combustion ◽  
Propyl Ketone ◽  
Parallel Fashion

In the slow combustion of 2-methyl-but-2-ene at ca . 250 °C, an initial pressure decrease, which represents the formation of peroxidic intermediates, is followed by an autocatalytic pressure increase during which little olefin is consumed and the main processes are break ­ down and further oxidation of primary reaction products. Acetone and acetaldehyde are the principal early non-peroxidic products and these are formed initially in equivalent quantities and in closely parallel fashion. Methyl iso propyl ketone is produced in somewhat smaller amounts and methyl alcohol, which appears comparatively late in the reaction, probably arises from the oxidation of acetaldehyde. The results suggest that the predominant mode of initial attack of the olefin is addition of oxygen to the double bond followed by decomposition of the resulting cyclic peroxides, although some hydroperoxylation also occurs.

Sign in / Sign up

Export Citation Format

Share Document