Bond strength alkane

Burkey and co-workers have reported high pressure photoacoustic results for alkane complex formation and further reaction wiA other nucleophiles with M = Cr and W."° They obtain overall AH° and AV° values and derive the M—alkane bond strengths that are 50 kJ mol" for both metals. 

Open-chain alkanes, alkyl halide reduction, 29-31 Organosilicon hydrides bond strengths, 5-6 hypervalent silicon species, 9-11 ionic hydrogenation, 5 trivalent silicon species, 7-9 Orthoesters, reduction of, 97-99 Oxime reduction, 102... 

The alcohols are intermediates in the formation of ketones. Isomerization of the products is not observed. Hydroxylation at the 2-position is favored over that at the 3-position, and the latter is preferred over hydroxylation at the 4-position. Solubility and concentration in the reaction medium, intrazeolite diffusion of the reactants, steric hindrance at the reactive carbon center, and C-H bond strength influence the reactivity and H202 selectivity (Table XXIV). The advantage of the large-pore Ti-beta over TS-1 in the oxidation of bulky alkane molecules is shown by the results in Table XXV. 

Excited-state Mg atoms react with methane and other alkanes via H atom abstraction in the gas phase (equation 1). By studying the vibrational states of the MgH product, information on the mechanism has been inferred. It has been found that regardless of the alkane, RH (and thus the C—H bond strength), the vibrational state distributions are essentially identical. This suggests that long-lived vibrationaUy excited [RMgH] complexes are not intermediates for equation 1 in the gas phase. The situation is quite different for excited-state Mg atoms reacting with methane under matrix conditions, where the insertion product (equation 2) is sufficiently stable for analysis via infrared spectroscopy ". Calcium atoms have been shown to insert into the C—H bonds of cycloalkanes. ... 

The hydroxyl radical will be the predominant entity which attacks the alkane to regenerate an alkyl radical (Reaction 10) under conditions where isomerization and decomposition are the usual fate of alkylperoxy radicals. The activation energy for attack on an alkane molecule by OH, although difficult to determine accurately (30), is low (I, 3) (1-2 kcal. per mole). This has an important consequence. The reaction will be unselective, being insensitive to C—H bond strength. Each and every alkyl radical derived from the alkane skeleton will therefore be formed. To describe the chain-propagation steps under conditions where isomerization is a frequent fate of alkylperoxy radicals it is necessary, then, to consider each and every alkylperoxy radical derived from the alkane and not just the tertiary radicals. 

Why is ethyne so much less stable than ethene or ethane First, C-C bonds are not as strong as C-H bonds. Therefore a gain in stability usually is to be expected when C-H bonds are made at the expense of C-C bonds ethene and ethane each have more C-H bonds than ethyne has. Second, ethyne has six electrons held between the two carbons and these electrons experience considerable mutual interelectronic repulsion. This accounts for the fact that the average C—C bond strength for the triple bond of an alkyne is 200/3 = 67 kcal, compared to 146/2 = 73 for the double bond of an alkene and 83 kcal for a normal single bond of an alkane. 

The bond length of a carbon triple bond is 1.20 A and the bond strength is 200 kcal mol-1. The n bonds are weaker than the a bond. The presence of the ji bonds explains why alkynes are more reactive than alkanes. 

The support induced changes in hydrogenolysis reactions of alkanes can be explained to a large extent by support induced changes in the Pt-H bond strength and hydrogen adsorption site on Pt. This can easily explain the well-known compensation effect found in the kinetics of the hydrogenolysis of alkanes catalyzed by supported metal catalysts. 

The bond strengths for the HF and HI bonds are 135 kcal/mol (565 kJ/mol) and 71 kcal/mol (297 kJ/mol), respectively. Explain why F2 reacts explosively with alkanes whereas I2 does not react at all. 

You may be confused the first time you see the IR spectrum of a terminal alkyne, R-OC-H, because you will see a strongish sharp peak at around 3300 cm"1 that looks just like an N-H stretch. The displacement of this peak from the usual C-H stretch at about 3000 cm"1 cannot be due to a change in the reduced mass and must be due to a marked increase in bond strength. The alkyne C-H bond is shorter and stronger than alkane C-H bonds. 

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