The Chlorine Atom Sensitized Oxidation and the Ozonolysis of C2Cl4

1974 ◽  
Vol 52 (23) ◽  
pp. 3852-3862 ◽  
Author(s):  
Eckart Mathias ◽  
Eugenio Sanhueza ◽  
I. C. Hisatsune ◽  
Julian Heicklen
Keyword(s):  
Free Radicals ◽  
Chain Length ◽  
Chlorine Atom ◽  
Chain Process ◽  
Chain Mechanism ◽  
A Chain ◽  
A Minor ◽  
Long Chain

The chlorine atom initiated oxidation of C2Cl4 was studied both in the absence and presence of O3 at 24 and 32 °C. In the absence of O3, the products are CCl3CCl(O) and CCl2O, and they are produced in a long-chain process in a ratio of 2.5 at 24 °C and 3.0 at 32 °C. The product producing step involves the decay of C2Cl5O radicals[Formula: see text]The ratio k6a/k6b is 5.0 at 24 °C and 6.0 at 32 °C since CCl3 reacts with O2 to produce another CCl2O molecule. In the presence of O3 the ratio Φ{CCl3CCl(O)}/Φ{CCl2O} drops, [Formula: see text] is produced, and the chain length is reduced. The change in Φ{CCl3CCl(O)}/Φ{CCl2O} is a function of [O3]/[O2] and is attributed to the additional reactions[Formula: see text]The epoxide yield is a function of [C2Cl4]/[O3] and is attributed to the reaction of ClO with C2Cl4. The ClO is produced by the reaction of Cl• with O3[Formula: see text]which competes with[Formula: see text]The ratio k2/kl0 = 6.7. The reduction in yield as O3 is added results from the terminating reaction[Formula: see text]The ClO2 reacts further with O3 to produce Cl2O7.The reaction of O3 with C2Cl4 at 24 °C also produces mainly CCl3CCl(O) and CCl2O with [Formula: see text] as a minor product. Other minor products detected after extended conversions included Cl2, CO, and CO2. However c-C3Cl6 was not found. The ratio [CCl3CCl(O)]/[CCl2O] is < 1. Moreover, the addition of O2 retarded the reaction, indicating a long chain mechanism in which both free radicals (species with an odd number of electrons) and CCl2 were absent. A diradical chain mechanism is presented which explains the main features. The chain step is the addition of CCl2O2 to C2Cl4[Formula: see text]The adduct then reacts with O3 in a chain regenerating step or with O2 in a chain terminating step.

THE PHOTOINITIATED HALOGENATION REACTIONS OF N-BROMOACETANILIDE AND N-BROMO-2,4,6-TRICHLOROACETANILIDE

1966 ◽  
Vol 44 (13) ◽  
pp. 1555-1562
Author(s):  
Dennis D. Tanner ◽  
Eugene Protz
Keyword(s):  
Carbon Tetrachloride ◽  
Bromine Atom ◽  
Benzyl Bromide ◽  
Chain Process ◽  
Chain Mechanism ◽  
Chain Component ◽  
Rearrangement Reaction ◽  
A Chain ◽  
Photoinduced Rearrangement ◽  
Long Chain

The photoinduced rearrangement reaction of N-bromoacetanilide to p-bromoacetanilide in carbon tetrachloride was found to have a quantum efficiency approaching unity, and evidence is presented to indicate a chain component to the reaction process whose product-determining species is either the mesomeric acetanilide radical or the bromine atom. It was demonstrated that small variations in the solvent composition affected the product ratio of p- to o-bromoacetanilide. The reaction of N-bromoacetanilide in carbon tetrachloride with added toluene was found to be a long-chain process producing p-bromoacetanilide as well as acetanilide and benzyl bromide. The bromination of toluene by N-bromo-2,4,6-trichloroacetanilide was shown to proceed by a chain mechanism involving the bromine radical as the chain-propagating species, and this mechanism is used as a model to explain the reaction of N-bromoacetanilide in dilute carbon tetrachloride solutions of toluene.

scholarly journals The mechanism of chain breaking in the thermal decomposition of ethane

1938 ◽  
Vol 167 (931) ◽  
pp. 439-446 ◽  
Author(s):  
J. E. Hobbs ◽  
Cyril Norman Hinshelwood
Keyword(s):  
Nitric Oxide ◽  
Thermal Decomposition ◽  
Free Radicals ◽  
Chain Length ◽  
Chain Mechanism ◽  
Collision Process ◽  
Ethane Molecule ◽  
Chain Breaking ◽  
The Mean ◽  
A Chain

The decomposition of ethane in the neighbourhood of 600° occurs largely by a chain mechanism in which free radicals are formed. In the course of experiments on the inhibition of the reaction by nitric oxide, Staveley (1937) found that the mean chain length diminished with increasing ethane pressure. From this he reached the conclusion that the chains were broken predominantly by a ternary collision process involving two radicles and an ethane molecule. The important question whether chains are ended by binary or by ternary collisions can be approached in another way, the exploration of which is described in the following pages.

The gaseous oxidation of aliphatic alcohols. III. n - and iso -propyl alcohols

1960 ◽  
Vol 257 (1290) ◽  
pp. 402-412 ◽  
Keyword(s):  
Hydrogen Peroxide ◽  
Carbon Monoxide ◽  
Free Radicals ◽  
Induction Period ◽  
Isopropyl Alcohol ◽  
Side Reactions ◽  
Chain Mechanism ◽  
Complete Elimination ◽  
Chain Branching ◽  
A Chain

A study of the gaseous oxidation of n -propyl alcohol (1-propanol) at 264°C shows that, after an induction period during which higher aldehydes and hydrogen peroxide are apparently the only products formed, the pressure starts to rise autocatalytically and methanol, formaldehyde and carbon monoxide become detectable. Additions of higher aldehydes reduce the induction period but the amounts required for its complete elimination are considerably greater than those normally present at the end of the induction period. A chain mechanism is proposed which involves initially abstraction of hydrogen from 1-propanol by HO 2 radicals followed by interaction of the resulting hydroxypropyl radicals with oxygen to yield propionaldehyde. Further reactions of this aldehyde are believed to be responsible for chain-branching and for the formation of the various C 1 products. Isopropyl alcohol (2-propanol) is much less readily oxidized than 1-propanol. At 330°C the main oxidation product is acetone which is formed together with hydrogen peroxide in somewhat smaller quantities. Minor products include methanol, acetaldehyde and formaldehyde. The course of the oxidation of 2-propanol is little affected by additions of acetone or formaldehyde but the induction period is markedly reduced by added acetaldehyde. The chain cycle suggested for the initial stages of oxidation involves attack by HO 2 radicals at the tertiary C─H bond of the alcohol followed by reaction of the resulting free radicals with oxygen to give acetone. The intermediate responsible for chain-branching is believed to be acetaldehyde which is produced by side reactions. C 1 compounds are formed partly by oxidation of this aldehyde and partly by further reactions of acetone.

Evidence for a mevalonate shunt in a tracheophyte

1985 ◽  
Vol 225 (1241) ◽  
pp. 425-444 ◽  
Keyword(s):  
Chain Length ◽  
Length Distribution ◽  
Specific Inhibitor ◽  
Leaf Tissue ◽  
Acetate Incorporation ◽  
Wheat Seedlings ◽  
Chain Length Distribution ◽  
A Chain ◽  
Coa Reductase ◽  
A Minor

Primary leaf tissue from light and dark grown wheat seedlings incubated with [2- 14 C]acetate and [2- 3 H]mevalonolactone (MVA) synthesized doubly labelled sterols and long chain fatty alcohols (LCFA). While [2- 3 H]MVA was incorporated into LCFA as efficiently as into sterols, [5- 3 H]MVA was metabolized only to sterols. Mevinolin, a specific inhibitor of HMG–CoA reductase, completely inhibited [2- 14 C]acetate incorporation into sterols but it did not completely prevent [2- 3 H]MVA from being incorporated into LCFA. In the presence and absence of mevinolin, 3 H in the purified LCFA was found associated primarily with C 22 , C 24 , and C 26 (components isolated from the subcellular membranes), while 14 C was present additionally in C 28 (the major LCFA isolated from the epicuticular wax). Substantial 14 C and 3 H was incorporated into the membrane-bound 24-desalkyl and 24-alkylsterols with no loss of label associated with increasing the side chain length, that is, by alkylation at C 24 . The results demonstrate for the first time that: (i) the MVA shunt operates in a tracheophyte; (ii) preferential utilization of acetate, formed by the shunt and presumably compartmentalized, may exist in wheat for the synthesis of LCFA having a chain length distribution more suitable for membrane than wax construction; and (iii) the MVA shunt is not a minor vestigial lipid pathway but may, under certain physiological and developmental conditions, represent a pathway for routing isopentenyl pyrophosphate C-atoms away from their inclusion into the sterol pathway. Photosynthesis had no apparent effect on shunt activity.

Oxidation-Reduction Systems for Initiation of Radical Processes. VI. Systems Involving Oxygen for Initiation of Oxidative Degradation of Polymers

1959 ◽  
Vol 32 (1) ◽  
pp. 231-243 ◽  
Author(s):  
E. I. Tinyakova ◽  
B. A. Dolgoplosk ◽  
V. N. Reĭkh
Keyword(s):  
Free Radicals ◽  
Low Temperatures ◽  
Oxidative Degradation ◽  
Chain Process ◽  
Iron Salts ◽  
Oxidation Reduction ◽  
A Chain ◽  
Radical Processes ◽  
Effective Source ◽  
Hydrocarbon Media

Abstract 1. The mechanism of action of various oxidation-reduction systems containing organic reducing agents, iron salts, and oxygen, is investigated, and it is shown that in hydrocarbon media these systems are an effective source of free radicals at low temperatures. 2. The possibility of utilization of these systems for initiation of a chain process of oxidative degradation of unsaturated and some saturated polymers, at low temperatures, is shown.

The Reaction of O(3P) with C2Cl4

1974 ◽  
Vol 52 (23) ◽  
pp. 3870-3878 ◽  
Author(s):  
Eugenio Sanhueza ◽  
Julian Heicklen
Keyword(s):  
Reaction Mechanism ◽  
Quantum Yield ◽  
Chain Length ◽  
Rate Coefficient ◽  
Chain Process ◽  
Reaction Conditions ◽  
Text Production ◽  
Competitive Kinetics ◽  
A Chain ◽  
Cl Atom

The reaction of O(3P), prepared from Hg photosensitization of N2O with C2Cl4 was studied at 25 °C. The exclusive products of the reaction in the absence of O2 were CCl2O and polymer (as well as N2 from the N2O). The quantum yield of CCl2O production, Φ{CCl2O}, was 0.19 independent of the C2Cl4 pressure or the absorbed intensity, Ia. There was no evidence for CO, Cl2, c-C3Cl6, CCl3CCl(O), or [Formula: see text] production. The reaction mechanism is[Formula: see text]with k12a/k12 = 0.19. The CCl2 radical dimerizes and the energetic C2Cl4O* intermediate polymerizes. By competitive kinetics, the ratio k12/k13 was found to be 0.10, where k12 ≡ k12a + k12b and k13 is the rate coefficient of the O(3P) + C2F4 reaction.In the presence of O2, a chain process is involved in which CCl3CCl(O) and CCl2O are the major products. They are formed in a ratio of 2.0 independent of reaction conditions, but the chain length is proportional to [C2Cl4]/Ia1/2. Also produced is CO with a quantum yield of ∼0.18. The ratio Φ{CCl3CCl(O)}/Φ{CCl2O} = 2.0 is similar to that of 2.5 found in the Cl atom initiated oxidation. This result is interpreted to mean that chlorine atoms are involved in the chain. The reaction which initiates monoradicals in the system is[Formula: see text]

Regulation of leptin secretion from white adipocytes by free fatty acids

2003 ◽  
Vol 285 (3) ◽  
pp. E521-E526 ◽  
Author(s):  
Philippe G. Cammisotto ◽  
Yves Gélinas ◽  
Yves Deshaies ◽  
Ludwik J. Bukowiecki
Keyword(s):  
Fatty Acids ◽  
Chain Length ◽  
Unsaturated Fatty Acids ◽  
Saturated Fatty Acids ◽  
Acid Oxidation ◽  
Mitochondrial Fatty Acid Oxidation ◽  
White Adipocytes ◽  
Mitochondrial Fatty Acid ◽  
A Chain ◽  
Long Chain

Norepinephrine stimulates lipolysis and concurrently inhibits insulin-stimulated leptin secretion from white adipocytes. To assess whether there is a cause-effect relationship between these two metabolic events, the effects of fatty acids were investigated in isolated rat adipocytes incubated in buffer containing low (0.1%) and high (4%) albumin concentrations. Palmitic acid (1 mM) mimicked the inhibitory effects of norepinephrine (1 μM) on insulin (10 nM)-stimulated leptin secretion, but only at low albumin concentrations. Studies investigating the effects of the chain length of saturated fatty acids [from butyric (C4) to stearic (C18) acids] revealed that only fatty acids with a chain length superior or equal to eight carbons effectively inhibited insulin-stimulated leptin secretion. Long-chain mono- and polyunsaturated fatty acids constitutively present in adipocyte triglyceride stores (oleic, linoleic, γ-linolenic, palmitoleic, eicosapentanoic, and docosahexanoic acids) also completely suppressed leptin secretion. Saturated and unsaturated fatty acids inhibited insulin-stimulated leptin secretion with the same potency and without any significant effect on basal secretion. On the other hand, inhibitors of mitochondrial fatty acid oxidation (palmoxirate, 2-bromopalmitate, 2-bromocaproate) attenuated the stimulatory effects of insulin on leptin release without reversing the effects of fatty acids or norepinephrine, suggesting that fatty acids do not need to be oxidized by the mitochondria to inhibit leptin release. These results demonstrate that long-chain fatty acids mimic the effects of norepinephrine on leptin secretion and suggest that they may play a regulatory role as messengers between stimulation of lipolysis by norepinephrine and inhibition of leptin secretion.

scholarly journals Neglected Very Long-Chain Hydrocarbons and the Incorporation of Body Surface Area Metrics Reveal Novel Perspectives for Cuticular Profile Analysis in Insects

Insects ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 83
Author(s):  
Marek Golian ◽  
Tanja Bien ◽  
Sebastian Schmelzle ◽  
Margy Alejandra Esparza-Mora ◽  
Dino Peter McMahon ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Chain Length ◽  
Body Surface ◽  
Profile Analysis ◽  
Analytical Techniques ◽  
Ionization Mass ◽  
Surface Areas ◽  
Length Range ◽  
A Chain ◽  
Long Chain

Most of our knowledge on insect cuticular hydrocarbons (CHCs) stems from analytical techniques based on gas-chromatography coupled with mass spectrometry (GC-MS). However, this method has its limits under standard conditions, particularly in detecting compounds beyond a chain length of around C40. Here, we compare the CHC chain length range detectable by GC-MS with the range assessed by silver-assisted laser desorption/ionization mass spectrometry (Ag-LDI-MS), a novel and rarely applied technique on insect CHCs, in seven species of the order Blattodea. For all tested species, we unveiled a considerable range of very long-chain CHCs up to C58, which are not detectable by standard GC-MS technology. This indicates that general studies on insect CHCs may frequently miss compounds in this range, and we encourage future studies to implement analytical techniques extending the conventionally accessed chain length range. Furthermore, we incorporate 3D scanned insect body surface areas as an additional factor for the comparative quantification of extracted CHC amounts between our study species. CHC quantity distributions differed considerably when adjusted for body surface areas as opposed to directly assessing extracted CHC amounts, suggesting that a more accurate evaluation of relative CHC quantities can be achieved by taking body surface areas into account.

scholarly journals Reaction chains in the thermal decomposition of hydrocarbons. A comparison of methane, ethane, propane and hexane

1938 ◽  
Vol 167 (931) ◽  
pp. 447-455 ◽  
Author(s):  
J. E. Hobbs ◽  
Cyril Norman Hinshelwood
Keyword(s):  
Nitric Oxide ◽  
Thermal Decomposition ◽  
Chain Length ◽  
Homologous Series ◽  
Normal Rate ◽  
Chain Mechanism ◽  
Reaction Proceeds ◽  
Decomposition Of Hydrocarbons ◽  
A Chain

The inhibition by nitric oxide of the thermal decomposition of ethane at 600° shows that the reaction proceeds partly by a chain mechanism, the apparent chain length, as measured by the ratio of the normal rate to that of the chain-free reaction, being of the order 5-15 over the range of pressure 50-500 mm., and falling with increasing pressure (Staveley 1937; Hobbs and Hinshelwood 1938). In passing up a homologous series of compounds the chain length may rise or fall. With the series of ethers, for examples, it decreases rapidly, whereas with the aldehydes it increases (Staveley and Hinshelwood 1937).

scholarly journals Integrated lipidomics and proteomics reveal cardiolipin alterations, upregulation of HADHA and long chain fatty acids in pancreatic cancer stem cells

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Claudia Di Carlo ◽  
Bebiana C. Sousa ◽  
Marcello Manfredi ◽  
Jessica Brandi ◽  
Elisa Dalla Pozza ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
Stem Cells ◽  
Fatty Acid ◽  
Cancer Stem Cells ◽  
Acyl Chain ◽  
Fatty Acid Elongase ◽  
Acyl Chains ◽  
A Chain ◽  
Pancreatic Cancer Stem Cells ◽  
Long Chain

AbstractPancreatic cancer stem cells (PCSCs) play a key role in the aggressiveness of pancreatic ductal adenocarcinomas (PDAC); however, little is known about their signaling and metabolic pathways. Here we show that PCSCs have specific and common proteome and lipidome modulations. PCSCs displayed downregulation of lactate dehydrogenase A chain, and upregulation of trifunctional enzyme subunit alpha. The upregulated proteins of PCSCs are mainly involved in fatty acid (FA) elongation and biosynthesis of unsaturated FAs. Accordingly, lipidomics reveals an increase in long and very long-chain unsaturated FAs, which are products of fatty acid elongase-5 predicted as a key gene. Moreover, lipidomics showed the induction in PCSCs of molecular species of cardiolipin with mixed incorporation of 16:0, 18:1, and 18:2 acyl chains. Our data indicate a crucial role of FA elongation and alteration in cardiolipin acyl chain composition in PCSCs, representing attractive therapeutic targets in PDAC.

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