Hydrogenation multiple bonds

As can be presumed from electronegativity of silicon and hydrogen, silanes serve as hydride donors. Triethylsilane hydrogenates multiple bonds of aldehydes, ketones, and olefins in the presence of trifluoroacetic acid or other catalysts (eq (31)) [28]. 

A H(detected)- C shift correlation spectrum (conmion acronym HMQC, for heteronuclear multiple quantum coherence, but sometimes also called COSY) is a rapid way to assign peaks from protonated carbons, once the hydrogen peaks are identified. With changes in pulse timings, this can also become the HMBC (l eteronuclear multiple bond coimectivity) experiment, where the correlations are made via the... 

Hydrogenation of Carbon-Carbon Multiple Bonds and Cyclopropane Rings... 

The commonly accepted mechanism of heterogeneously catalyzed hydrogenation involves activation of both the hydrogen and the C—C multiple bond adsorbed on the metal surface. First one hydrogen atom is transferred to the least hindered position of the multiple bond to give a half-hydrogenated adsorbed species. This reaction is fully reversible and ac-... 

As portrayed m Figure 2 20 the two carbons of acetylene are connected to each other by a 2sp-2sp cr bond and each is attached to a hydrogen substituent by a 2sp-ls CT bond The unhybndized 2p orbitals on one carbon overlap with their counterparts on the other to form two rr bonds The carbon-carbon triple bond m acetylene is viewed as a multiple bond of the ct + rr + rr type... 

The relationship between reactants and products m addition reactions can be illustrated by the hydrogenation of alkenes to yield alkanes Hydrogenation is the addition of H2 to a multiple bond An example is the reaction of hydrogen with ethylene to form ethane... 

The relatronshrp between molecular formulas multiple bonds and nngs rs referred to as the index of hydrogen deficiency and can be expressed by the equatron... 

Heat of hydrogenation (Section 6 1) Heat evolved on hydro genation of a substance It is the value of — A//° for the ad dition of H2 to a multiple bond... 

Electrochemical Fluorination. In the Simons electrochemical fluorination (ECF) process the organic reactant is dissolved in anhydrous hydrogen fluoride and fluorinated at the anode, usually nickel, of an electrochemical ceU. This process has been reviewed (6). Essentially all hydrogen atoms are substituted by fluorine atoms carbon—carbon multiple bonds are saturated. The product phase is heavier than the HF phase and insoluble in it and is recovered by phase separation. 

Oxidation. The oxidation reactions of organoboranes have been reviewed (5,7,215). Hydroboration—oxidation is an anti-Markovnikov cis-hydration of carbon—carbon multiple bonds. The standard oxidation procedure employs 30% hydrogen peroxide and 3 M sodium hydroxide. The reaction proceeds with retention of configuration (216). 

Nitriles. Nitriles can be prepared by a number of methods, including ( /) the reaction of alkyl haHdes with alkaH metal cyanides, (2) addition of hydrogen cyanide to a carbon—carbon, carbon—oxygen, or carbon—nitrogen multiple bond, (2) reaction of hydrogen cyanide with a carboxyHc acid over a dehydration catalyst, and (4) ammoxidation of hydrocarbons containing an activated methyl group. For reviews on the preparation of nitriles see references 14 and 15. 

From Cg/ZgNO (problem 4), for example, the empirical formula C Hjo is derived and compared with the alkane formula Cc>H2o, a hydrogen deficit of ten and thus of five double-bond equivalents is deduced. If the NMR spectra have too few signals in the shift range appropriate for multiple bonds, then the double-bond equivalents indicate rings (see, for example, a-pinene. Fig. 2.4). 

In general, each ting or double bond in a molecule corresponds to a loss of two hydrogens from the alkane formula ChH2/1+2- Knowing this relationship, it s possible to work backward from a molecular formula to calculate a molecule s degree of unsaturation—the number of rings and/or multiple bonds present in the molecule. 

In an unsaturated hydrocarbon, at least one of the carbon-carbon bonds in the molecule is a multiple bond. As a result, there are fewer hydrogen atoms in an unsaturated hydrocarbon than in a saturated one with the same number of carbons. We will consider two types of unsaturated hydrocarbons—... 

At this stage it is helpful to know that compounds of hydrogen and carbon are called hydrocarbons. They include methane, CH4 (1) ethane, C2H6 (2) and benzene, C6H6 (3). Hydrocarbons that have no carbon-carbon multiple bonds are called alkanes. Thus, methane and ethane are both alkanes. The unbranched alkanes with... 

A saturated hydrocarbon is an aliphatic hydrocarbon with no multiple carbon-carbon bonds an unsaturated hydrocarbon has one or more double or triple carbon-carbon bonds. More hydrogen atoms can be added to compounds in which there are multiple bonds, but compounds with only single bonds are saturated with hydrogen. Compound (3) is saturated compounds (4) and (5) are unsaturated. 

Mond process The purification of nickel by the formation and decomposition of nickel carbonyl, monomer A small molecule from which a polymer is formed. Examples CH2=CH2 for polyethylene NH2(CH2)6NH2 for nylon, monoprotic acid A Bronsted acid with one acidic hydrogen atom. Example CH COOI I. monosaccharide An individual unit from which carbohydrates are considered to be composed. Example C6H(206, glucose, multiple bond A double or triple bond between two atoms. 

The addition is therefore stereospecifically syn and, like catalytic hydrogenation, generally takes place from the less-hindered side of a double bond, though not much discrimination in this respect is observed where the difference in hulk effects is small.Diimide reductions are most successful with symmetrical multiple bonds (C=C, C=C, N=N) and are not useful for those inherently polar (C=N, C=N, C=0, etc.). Diimide is not stable enough for isolation at ordinary temperatures, though it has been prepared as a yellow solid at — 196°C. 

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