Carbon skeleton adding carbons

A certain species of grasshopper secretes an allenic substance of molecular formula C13H20O3 that acts as an ant repellent The carbon skeleton and location of various substituents in this substance are indicated in the partial structure shown Complete the structure adding double bonds where appropriate... 

Mastery of tetrasubstituted olefins greatly expands the tools available for the synthesis of chiral carbon skeletons and tetrasubstituted olefins have the added value of possibly creating two stereogenic centers simultaneously. 

Literature data on the carbon skeleton elongation may be classified according to the number of carbon atoms added. Such a classification, although far from being ideal, is useful from the synthetic viewpoint. Scheme 2 illustrates the usefulness of a-amino acids (in particular a-amino-(3-hydroxy acids e.g., serine, threonine, and their homologues) in the synthesis of amino sugars. 

Monohydnc alcohols are named by adding -01 to a molecular skeleton name. Carbon chains, unsaturation, etc., are numbered in a manner analogous to that used for carboxylic adds. (See preceding section.)... 

A compound possessing a carbon skeleton with certain side chains is not named as a derivative of another compound possessing a carbon skeleton with fewer side chains when the "added" one or more side chains in the first compound are identical to side chains present in the second compound. When the "added" side chains are not identical, the first compound, other things being equal, is named as a derivative of the second ... 

Functional Group Transformations Functional group transformations help us in the conversion of a functional group to an aldehyde or a ketone without affecting the carbon skeleton of the molecule. Aldehydes can be synthesised by the oxidation of primary alcohols, or by the reduction of esters, acid chlorides, or nitriles. Since nitriles can be obtained from alkyl halides, this a way of adding an aldehyde unit (CHO) to an alkyl halide ... 

When the hydrogen transferred as hydride to the cofactor is retransferred to the same carbon atom in the product, the movement is far more difficult to detect. The conversion of D-glucose 6-phosphate (58) into lL-mt/o-inositol 1-phosphate (61) occurs by cyclization of the carbon skeleton, with formation of a new bond between C-l and C-6. When each carbon atom in turn was specifically labeled with tritium, there was complete retention of tritium, even in the presence of added NADH, although there was an apparent, small isotope-effect with D-glucose-5-t 6-phosphate.19 The mechanism proposed for the cyclization19 was an initial oxidation at C-5 to give NADH and xylo-hexos-5-ulose 6-phosphate (59), followed by an aldol reaction causing cyclization to lL-myo-inosose-2 1-phosphate (60), which is then... 

Many simple common compounds are known by both a trivial and a systematic name. The systematic names are helpful in learning the structures of organic compounds, but the trivial names are often simpler and can reflect the source or dominant reactivity of the compound concerned. The systematic name for a compound has a stem that describes the carbon skeleton, prefixes and suffixes that indicate the functional groups, and numbers (locants) that define their position. Prefixes may also be added to indicate modifications to the carbon skeleton and to define the stereochemistry. A list of the more common prefixes, suffixes and stems is given in Table 1.2. 

Figure 2 shows that the C1-C5 aliphatic hydrocarbons, amino acids, carboxylic acids, and sulfonic acids from the Murchison meteorite appear to follow a common trend when their values are plotted against carbon number, values generally decrease as the amount of carbon in the molecules increases. This trend has been interpreted as the result of a kinetic isotope effect during the sequential formation of higher-molecular-weight compounds from simpler precursors (Yuen et al., 1984). The more reactive is preferentially added during the synthesis of the carbon skeleton of these compounds. 

A corollary of this statement is the following If these polyaromatic or polycyclic saturated structures are present in the carbon skeleton of coal, they should be identified in the short-contact-time liquefaction products. The possibility of some isomerization reactions in the carbon skeleton cannot be excluded totally, but the most important fact is that no dramatic aromatization of hydroaromatic rings or saturation of aromatic rings takes place under these conditions. Many of the chemical functions also are stable under these conditions, especially the O, S, and N heterocyclic aromatic structures. Water formation by phenol dehydroxylation is minimal. In coal liquefaction under our conditions, even at long reaction times (up to 90 min) in the absence of an added catalyst, the -OH bonded to a monoaromatic ring is stable. Under the same conditions, dehydroxylation of polyaromatic phenols does occur (10). 

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