One-carbon molecules

Nagiev, T.M. and Gasanova, L.M., Thes. Rep. All-Union Meeting on Chemical Synthesis Based on One-Carbon Molecules, Nauka, Moscow, 1984, p. 73 (in Russian). 

Formaldehyde is a simple one-carbon molecule and is rapidly absorbed and metabolized by animals, including humans. A thorough review of the available literature failed to produce any reliable biomarkers of exposure to formaldehyde. 

The chemistry of one-carbon molecules (better known as Cj chemistry) is a very exciting area of research for the organometallic chemist. The motivation for these efforts stems from the belief that the raw material base for commercial organic chemicals will shift from oil to coal, in the near future, due to the decline of petroleum reserves. 

In alcoholic fermentation, each three-carbon molecule that is produced during glycolysis is split to form a two-carbon molecule—the alcohol ethanol—and a one-carbon molecule, carbon dioxide. Two molecules of ATP are produced during glycolysis. ... 

Int. Symposium Catal. React, of one Carbon Molecules , Bruges Belgium, 1982. 

He tries to determine the conjuncture which could be created by a molecule mass of a substance with a bigger role than sulfur or phosphor, namely the carbon. The volume of the carbonic acid was equal with the one of the oxygen which enter in the composition, then, ifone should admit that the carbon volume, supposedly gaseous, which forms the other element, is double by the division of molecules in two, same as this type of combination, it might be necessary to assume that this volume is half of the one of oxygen with which is combined, and therefore the carbonic acid results from the union of one carbon molecule and two oxygen molecules. 

The electrooxidation of simple one-carbon molecules (Ci molecules), such as methanol, formaldehyde, and formic acid, became the subject of considerable and continuous interest. This is quite reasonable since these compounds, particularly methanol, are potential fuels for fuel cells. The complete oxidation of the... 

In addition to CH3X, other substituted molecules are possible in which more than one hydrogen is replaced by another atom or group of atoms. Thus, even for one-carbon molecules, there are many possible substituted structures. 

The proceedings of a symposium on Catalytic Reactions of One Carbon Molecules and a review which includes homogeneous catalysis with syn gas (i.e., H2 + CO) and metal clusters summarize recent developments in this area. ... 

J. Mol Catal, 17, 117<-401 (1982). (International Symposium of Catalytic Reactions of One-carbon Molecules (Belgium, June 1982).)... 

An unusual feature in the mass spectrum of methane is a small (1.1%) peak at m/z = 17 it is designated (M + 1) . How is it possible to have an ion present that has an extra mass unit The answer lies in the fact that carbon is not isotopically pure. About 1.1% of natural carbon is the isotope (see Table 10-1), giving rise to the additional peak. In the mass spectrum of ethane, the height of the (M + 1) peak, at m/z = 31, is about 2.2% that of the parent ion. The reason for this finding is statistical. The chance of finding a atom in a compound containing two carbons is double that expected of a one-carbon molecule. For a three-carbon moiety, it would be threefold, and so on. 

Both have reasonable mechanisms, but we prefer (b) because it introduces more simphfication. Route (a) simply ehops off one carbon atom and leaves us with a new target almost as difficult to make as TM 16. Route (b) however breaks the molecule into two more equal pieces -acetone and cyclohexyl bromide. 

Strategy Problem 6 A labelled compound for biosynthetic studies. Mevaloitic acid (TM 418) is an intermediate in the biosynthesis of terpenes and steroids (Tedder, volume 4, p.217 ff). To study exactly what happens to each carbon atom during its transformation into, say, hmonene (418A), we need separate samples of mevalonic acid labelled with in each carbon atom in the molecule. This turns our normal strategy on its head since we must now look for one carbon discoimections. You can use reagents like Na CN, and... 

Organic molecules m which one carbon atom is common to two rings are called spirocyclic compounds The simplest spirocyclic hydrocarbon is spiropentane a product... 

Figure 10 12 shows the interaction between the HOMO of one ethylene molecule and the LUMO of another In particular notice that two of the carbons that are to become ct bonded to each other m the product experience an antibondmg interaction during the cycloaddition process This raises the activation energy for cycloaddition and leads the reaction to be classified as a symmetry forbidden reaction Reaction were it to occur would take place slowly and by a mechanism m which the two new ct bonds are formed m separate steps rather than by way of a concerted process involving a sm gle transition state... 

Monomer (Section 6 21) The simplest stable molecule from which a particular polymer may be prepared Monosaccharide (Section 25 1) A carbohydrate that cannot be hydrolyzed further to yield a simpler carbohydrate Monosubstituted alkene (Section 5 6) An alkene of the type RCH=CH2 in which there is only one carbon directly bonded to the carbons of the double bond Multiplicity (Section 13 7) The number of peaks into which a signal IS split in nuclear magnetic resonance spectroscopy Signals are described as singlets doublets triplets and so on according to the number of peaks into which they are split... 

One of the major difficulties with molecular mechanics procedures (MMh- or otherwise) is that they almost always fail. That is, you find that force constants are not available for the molecule of interest. This is both the strength and weakness of molecular mechanics it uses atom types to introduce specific chemical environments for the atoms within a molecule (to obtain accuracy in the calculations) but then requires knowledge of force constants specific to that chemical environment (as specific as stating that an atom is in a five-member ring containing one oxygen and one carbon, for example). As the number, N, of atom types rises the number of force constants needed to describe all possible occurrences of these atom type becomes very large. For torsions, for... 

Quantum mechanical calculations generally have only one carbon atom type, compared with the many types of carbon atoms associated with a molecular mechanics force field like AMBER. Therefore, the number of quantum mechanics parameters needed for all possible molecules is much smaller. In principle, very accurate quantum mechanical calculations need no parameters at all, except fundamental constants such as the speed of light, etc. 

Atoms combine in definite proportions to give molecules. For example, natural gas is mostly composed of methane, a substance in which four hydrogen atoms (H) are combined with one carbon (C) the molecular formula is written as CH4. Similarly, water, ammonia, ethanol, and glucose have... 

Steam Reforming Processes. In the steam reforming process, light hydrocarbon feedstocks (qv), such as natural gas, Hquefied petroleum gas, and naphtha, or in some cases heavier distillate oils are purified of sulfur compounds (see Sulfurremoval and recovery). These then react with steam in the presence of a nickel-containing catalyst to produce a mixture of hydrogen, methane, and carbon oxides. Essentially total decomposition of compounds containing more than one carbon atom per molecule is obtained (see Ammonia Hydrogen Petroleum). 

Figure 1.2 Proteins are built up by amino acids that are linked by peptide bonds to form a polypeptide chain, (a) Schematic diagram of an amino acid. Illustrating the nomenclature used in this book. A central carbon atom (Ca) is attached to an amino group (NH2), a carboxyl group (COOH), a hydrogen atom (H), and a side chain (R). (b) In a polypeptide chain the carboxyl group of amino acid n has formed a peptide bond, C-N, to the amino group of amino acid + 1. One water molecule is eliminated in this process. The repeating units, which are called residues, are divided into main-chain atoms and side chains. The main-chain part, which is identical in all residues, contains a central Ca atom attached to an NH group, a C =0 group, and an H atom. The side chain R, which is different for different residues, is bound to the Ca atom.

If a molecule contains several asymmetric C atoms, then the diastereomers show diastereotopic shifts. Clionasterol (28a) and sitosterol (28b) for example, are two steroids that differ only in the absolute configuration at one carbon atom, C-24 Differing shifts of C nuclei close to this asymmetric C atom in 28a and b identify the two diastereomers including the absolute configuration of C-24 in both. The absolute configurations of carboxylic acids in pyrrolizidine ester alkaloids are also reflected in diastereotopic H and C shifts which is used in solving problem 54. 

Polycarbonates have also been prepared from diphenyl compounds where the benzene rings are separated by more than one carbon atom. In the absence of bulky side groups such polymer molecules are more flexible and crystallise very rapidly. As is to be expected, the more the separating carbon atoms the lower the melting range. This effect is shown in data supplied by Sehnell" Table 20.11). 

FIGURE 18.5 The reactive sites in aldol addition are the carbonyl group of one aldehyde molecule and the a-carbon atom of another. 

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