Double bond

About: Double bond is a research topic. Over the lifetime, 29147 publications have been published within this topic receiving 425077 citations.

Catalyzed Addition of Aldehydes to Activated Double Bonds—A New Synthetic Approach

Abstract: In the presence of cyanide ions as catalyst, aromatic and heterocyclic aldehydes can be smoothly added to α,β-unsaturated ketones, esters, and nitriles in aprotic solvents to form γ-diketones, 4-oxo carboxylic esters, and 4-oxo nitriles. Thiazolium salts in the presence of bases are also suitable catalysts; they permit not only addition of aromatic and heterocyclic aldehydes but also the addition of aliphatic aldehydes.

Chemical Basis of the Sulfo-phospho-vanillin Reaction for Estimating Total Serum Lipids

Abstract: Results with the "sulfo-phospho-vanillin" reaction, much used for determining total serum lipids, have been favorably compared with those for the gravimetric method. We investigated the basic chemistry of the reaction and determined the reactivity of this single reagent with various lipids. Our results suggest that: ( a ) The reaction requires a carbon-carbon double bond. ( b ) Concentrated sulfuric acid reacts with unsaturated lipids in the initial step to form a carbonium ion. ( c ) Phosphoric acid reacts with vanillin to produce a phosphate ester, with a resulting increase in the reactivity of the carbonyl group. ( d ) The carbonium ion reacts with the carbonyl group of phosphovanillin to form a colored compound, which is stabilized by resonance. ( e ) Unsaturated compounds with more than one double bond react, but reaction may vary with steric hindrance. ( f ) The method is reasonably precise, but its accuracy depends primarily on the reference standard used.

Crystal structure of naphthalene dioxygenase: side-on binding of dioxygen to iron.

Abstract: Binding of oxygen to iron is exploited in several biological and chemical processes. Although computational and spectroscopic results have suggested side-on binding, only end-on binding of oxygen to iron has been observed in crystal structures. We have determined structures of naphthalene dioxygenase that show a molecular oxygen species bound to the mononuclear iron in a side-on fashion. In a complex with substrate and dioxygen, the dioxygen molecule is lined up for an attack on the double bond of the aromatic substrate. The structures reported here provide the basis for a reaction mechanism and for the high stereospecificity of the reaction catalyzed by naphthalene dioxygenase.