Bond, chemical double

One of the most important publications on this subject, considered frorn the chemical side, is that of Gertrude Woker. This investigator drew attention to the importance of multiple bonding. The double bond is often accompanied by a pleasant, but the triple or acetylenic linkage generally produces a disagreeable smell a multiplicity of double bond can produce an effect equivalent to a triple bond. 

Isobutane is a compound in a class of chemicals called alkanes. Alkanes are chains of carbon atoms where each carbon atom has as many hydrogen atoms attached as possible. This means that all of the bonds between carbon atoms are single bonds (no double bonds). Such a molecule is said to be saturated. 

Lyases (class 4, often also referred to as synthases ) catalyze reactions involving either the cleavage or formation of chemical bonds, with double bonds either arising or disappearing. 

Lisinopril (S) -1-A - (l-Carboxy-3-phenylpropyl) -L-lysyl] L-proline dihydrate Pd-catalyzed carbonylation, hydroxylation of a double bond, chemical resolution, amidation, A-protection (using trifluoroacetic anhydride), carbonyl activation (using phosgene)... 

Free pyrimidines and purines are weakly basic compounds and are thus called bases. They have a variety of chemical properties that affect the structure, and ultimately the function, of nucleic acids. The purines and pyrimidines common in DNA and RNA are highly conjugated molecules (Fig. 8-2), a property with important consequences for the structure, electron distribution, and fight absorption of nucleic acids. Resonance among atoms in the ring gives most of the bonds partial double-bond character. One result is that pyrimidines are planar molecules purines are very nearly... 

Double bond - A double union of two carbon atoms instead of one union. Materials containing double bonds are chemically unsaturated. 

The Reduction Reactions. The object of the next three reactions (steps 4 to 6 in fig. 18.12a) is to reduce the 3-carbonyl group to a methylene group. The carbonyl is first reduced to a hydroxyl by 3-ketoacyl-ACP reductase. Next, the hydroxyl is removed by a dehydration reaction catalyzed by 3-hydroxyacyl-ACP dehydrase with the formation of a trans double bond. This double bond is reduced by NADPH catalyzed by 2,3-trans-enoyl-ACP reductase. Chemically, these reactions are nearly the same as the reverse of three steps in the j6-oxidation pathway except that the hydroxyl group is in the D-configuration for fatty acid synthesis and in the L-configuration for /3 oxidation (compare figs. 18.4a and 18.12a). Also remember that different cofactors, enzymes and cellular compartments are used in the reactions of fatty acid biosynthesis and degradation. 

If the four carbons are in a row, there must be one double bond in order to satisfy the requirement that each carbon have four chemical bonds. The double bond occurs either in the center of the molecule or toward an end. If in the center, two geometrical isomers occur with different positions of the terminal carbons relative to the double bond. In the latter case, two structural isomers occur differing in the extent of the branching within the carbon skeleton. Additional possibilities are ring structures. 

Structural formula A chemical formula that shows how the atoms of a molecule or polyatomic ion are arranged and the kinds of bonds (single, double on triple). 

Acetoxylation of alkenes takes place in allylic position [40,115], concurrent with addition of acetoxy groups across the double bond or double-bond system. The mechanism is almost certainly analogous to that discussed previously for methoxylation [Eq. (20)]. Because AcO is difficult to oxidize, the anodic discharge of simple, unactivated alkenes may be achieved in its presence. Subsequent reactions of the cationic intermediates are not very selective, but several experimental parameters may be controlled and the method can compare well with the few competing chemical methods. 

The chemical properties of a diene depend upon the arrangement of its double bonds. Isolated double bonds exert little effect on each other, and hence each reacts as though it w/ere the only double bond in the molecule. Except for the consumption of larger amounts of reagents, then, the chemical properties of the non-conjugated dienes are identical with those of the simple alkenes. 

Figure 6 The structure of NaC102,3H20. The water oxygens and one of the oxygens of CIOJ form a distorted octahedron around the sodium ion. Thin lines represent hydrogen bonds, heavy solid lines the O—H and O—Cl chemical bonds, and double lines describe the octahedron of oxygens in van der Waals contact with the sodium (Reproduced by permission from Acta Cryst., 1975, B31, 2146)...

The chemical structure of benzene remained one of the great mysteries in chemistry for nearly half a century. The compound s formula, C6H6, suggests that it contains three double bonds. A double bond consists of four electrons that hold two atoms in close proximity to each other in a molecule. Yet benzene has none of the chemical properties common to double-bonded substances. The solution to this problem was suggested in 1865 by the German chemist Friedrich August Kekule (1829-1896). Kekule suggested that the six... 

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