Discovery of benthol A and its challenging stereochemical assignment: opening up a new window for skeletal diversity of super-carbon-chain compounds

Discoveries of large new organic molecules in space help provide a foundation for understanding the role of the chemical bond and organic chemistry on a cosmic scale, and by extension, an opportunity to begin to address the interesting but far more complicated questions of chemical and biological origins and the issues that relate to them. Most of the organic molecules so far detected in the interstellar gas and circumstellar shells by radio telescopes are highly unsaturated carbon chains, a configuration of linear carbon which is unstable at high density, and therefore unfamiliar on Earth. For this reason laboratory detection until quite recently has lagged behind astronomical discovery of many new carbon molecules. The application of Fourier transform microwave spectroscopy to supersonic molecular beams has now largely overcome this obstacle, yielding in just over three years the laboratory detection of forty-four new carbon chains and eight new carbon ring-chains and rings, including two rhomboidal isomers of SiC3. The set consists of 14 polyynes, 20 carbon chain radicals, and 18 free carbenes. For four other triplet chains HC7H, HC9H, HC11H, and HC13H, which by symmetry are nonpolar, strong electronic spectra have been measured in the gas-phase by cavity ringdown absorption spectroscopy. Almost all of these molecules are good candidates for detection in space, and six in fact have now been detected in at least one astronomical source with large radio telescopes during the past two years. The laboratory astrophysics of the entire set is complete for the time being, in the sense that nearly all the rotational transitions of interest to radio astronomy can be calculated to a small fraction of 1 km sec–1 in equivalent radial velocity. With powerful new radio facilities planned or under construction it would be surprising if many more could not eventually be found. For each of the four new symmetric chains detected in the visible, the wavelength of the origin band has been measured to high accuracy, permitting deliberate searches for these molecules in diffuse and translucent molecular clouds.

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

10.26434/chemrxiv.7064474 ◽

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>

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

Proceedings of the British Society of Animal Science ◽

10.1017/s1752756200592977 ◽

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

Journal of Tribology ◽

10.1115/1.2920932 ◽

1992 ◽

Vol 114 (4) ◽

pp. 653-658 ◽

Cited By ~ 11

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.

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

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2002835117 ◽

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.

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

Rubber Chemistry and Technology ◽

10.5254/1.3546354 ◽

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:

Colopsinols D and E, New Polyhydroxyl Linear Carbon Chain Compounds from Marine Dinoflagellate Amphidinium sp.

Chemical and Pharmaceutical Bulletin ◽

10.1248/cpb.48.1447 ◽

2000 ◽

Vol 48 (10) ◽

pp. 1447-1451 ◽

Cited By ~ 16

Author(s):

Takaaki KUBOTA ◽

Masashi TSUDA ◽

Miho TAKAHASHI ◽

Masami ISHIBASHI ◽

Seiko OKA ◽

...

Keyword(s):

Carbon Chain ◽

Marine Dinoflagellate ◽

Chain Compounds ◽

Linear Carbon Chain

ChemInform Abstract: Colopsinols D and E, New Polyhydroxyl Linear Carbon Chain Compounds from Marine Dinoflagellate Amphidinium sp.

ChemInform ◽

10.1002/chin.200111197 ◽

2001 ◽

Vol 32 (11) ◽

pp. no-no

Author(s):

Takaaki Kubota ◽

Masashi Tsuda ◽

Miho Takahashi ◽

Masami Ishibashi ◽

Seiko Oka ◽

...

Keyword(s):

Carbon Chain ◽

Marine Dinoflagellate ◽

Chain Compounds ◽

Linear Carbon Chain

Cuticle hydrocarbons in saline aquatic beetles

10.7287/peerj.preprints.2967 ◽

2017 ◽

Author(s):

María Botella-Cruz ◽

Adrián Villastrigo ◽

Susana Pallarés ◽

Elena López-Gallego ◽

Andrés Millán ◽

...

Keyword(s):

Cuticular Hydrocarbons ◽

Aquatic Insects ◽

Selection Pressure ◽

Principal Component ◽

Carbon Chain ◽

Carbon Chain Length ◽

Gas Chromatograph ◽

Aquatic Beetles ◽

Branched Alkanes ◽

Chain Compounds

Hydrocarbons are the principal component of insects cuticle and play an important role in maintaining water balance. Cuticular impermeability could be an adaptative response to salinity and desiccation in aquatic insects; however, cuticular hydrocarbons have been poorly explored in this group and there are no previous data on saline species. We characterized cuticular hydrocarbons of adults and larvae of two saline aquatic beetles, namely Nebrioporus baeticus (Dytiscidae) and Enochrus jesusarribasi (Hydrophilidae), using a gas chromatograph coupled to a mass spectrometer. The CHC profile of adults of both species, characterized by a high abundance of branched alkanes and low of unsaturated alkenes, seems to be more similar to that of some terrestrial beetles (e.g. desert Tenebrionidae) compared with other aquatic Coleoptera (freshwater Dytiscidae). Adults of E. jesusarribasi had longer chain compounds than N. baeticus, in agreement with their higher resistance to salinity and desiccation. The more permeable cuticle of larvae was characterized by a lower diversity in compounds, shorter carbon chain length and a higher proportion of unsaturated hydrocarbons compared with that of the adults. These results suggest that osmotic stress on aquatic insects could exert a selection pressure on CHC profile similar to aridity in terrestrial species.

A THEORETICAL STUDY OF CARBON CHAINS OF TYPE CNF(N = 1–7) IN NEUTRAL AND IONIC FORMS

Journal of Theoretical and Computational Chemistry ◽

10.1142/s0219633611006815 ◽

2011 ◽

Vol 10 (06) ◽

pp. 789-802 ◽

Cited By ~ 2

Author(s):

HUI-FEN CHEN ◽

YU-JONG WU

Keyword(s):

Ionization Potential ◽

Electron Affinity ◽

Theoretical Study ◽

Ground States ◽

Carbon Chain ◽

Binding Energies ◽

Molecular Properties ◽

Neutral Species ◽

Carbon Chains ◽

Ionic Forms

The structures, binding energies, and molecular parameters of C n F clusters (n = 1–7) have been investigated theoretically on neutral and ionic forms with the RCCSD(T)//B3LYP/aug-cc-pVTZ level of theory. It can be concluded that for the ground states the linear structures are stable only for CF , C 6 F , and C 7 F . Other neutral species of C n F (n = 2–5) are slightly bent. The variation in stability with growth of the carbon chain is flat but the ionization potential and electron affinity exhibit clear variations with the size of the clusters. Cation clusters with an even n value have triplet ground states whereas singlet ground states exist when n is odd. All anions except CF -, have singlet ground states. The alternation in stability is found in both cationic and anionic forms, but the trends are reversed. Predictions of several molecular properties may be useful in the identification of these species in the laboratory and in space.