Hydrogen secondary

A single secondary hydrogen m butane is abstracted by a chlorine atom 3 9 times faster than a single primary hydrogen... 

Photochemical chlorination of pentane gave a mixture of three isomenc monochlorides The pnncipal monochlonde constituted 46% of the total and the remaining 54% was approximately a 1 1 mixture of the other two isomers Write structural formulas for the three monochlonde iso mers and specify which one was formed in greatest amount (Recall that a secondary hydrogen is abstracted three times faster by a chlonne atom than a pnmary hydrogen)... 

Polybutadiene and polyunsaturated fats, which contain aHyUc hydrogen atoms, oxidize more readily than polypropylene, which contains tertiary hydrogen atoms. A linear hydrocarbon such as polyethylene, which has secondary hydrogens, is the most stable of these substrates. 

The value of k /k can be determined by measuring the ratio of the products 1-chlorobutane 2-chlorobutane during the course of the reaction. A statistical correction must be made to take account of the fact that the primary hydrogens outnumber the secondaiy ones by 3 2. This calculation provides the relative reactivity of chlorine atoms toward the primary and secondary hydrogens in butane ... 

A primary allylic hydrogen at the ene 1 is especially reactive a secondary hydrogen migrates less facile, and a tertiary one is even less reactive. The enophile unit should be of an electron-poor nature it can consist of a carbon-carbon double or triple bond, a carbonyl group or an azo group. Mixtures of regioisomeric products may be obtained with substituted enophiles. The acrylic ester 6 reacts with... 

Propane is a more reactive paraffin than ethane and methane. This is due to the presence of two secondary hydrogens that could be easily substituted (Chapter 6). Propane is obtained from natural gas liquids or from refinery gas streams. Liquefied petroleum gas (LPG) is a mixture of propane and butane and is mainly used as a fuel. The heating value of propane is 2,300 Btu/ft. LPG is currently an important feedstock for the production of olefins for petrochemical use. 

A major use of propane recovered from natural gas is the production of light olefins by steam cracking processes. However, more chemicals can be obtained directly from propane by reaction with other reagents than from ethane. This may be attributed to the relatively higher reactivity of propane than ethane due to presence of two secondary hydrogens, which are easily substituted. 

The chemistry of n-butane is more varied than that of propane, partly because n-butane has four secondary hydrogen atoms available for substitution and three carbon-carbon bonds that can be cracked at high temperatures ... 

Chlorination of n-paraffins (C10-C14) in the liquid phase produces a mixture of chloroparaffins. Selectivity to monochlorination could be increased by limiting the reaction to a low conversion and by decreasing the chlorine to hydrocarbon ratio. Substitution of secondary hydrogen predominates. The reaction may be represented as ... 

From these and similar reactions, it s possible to calculate a reactivity order toward chlorination for different sorts of hydrogen atoms in a molecule. Take the butane chlorination, for instance. Butane has six equivalent primary hydrogens (-CH3) and four equivalent secondary hydrogens (-CH2-). The fact that butane yields 30% of 1-chlorobutane product means that each one of the six primary hydrogens is responsible for 30% -e 6 = 5% of the product. Similarly, the fact that 70% of 2-chlorobutane is formed means that each of the four secondary hydrogens is responsible for 70% -e 4 = 17.5% of the product. Thus, reaction of a secondary hydrogen happens 17.5% + 5% = 3.5 times as often as reaction of a primary hydrogen. 

Schiffbase, 1147 Scurvy vitamin C and, 772 sec-Butyl group, 84 Second-order reaction, 363 Secondary alcohol, 600 Secondary amine, 917 Secondary carbon, 84 Secondary hydrogen. 85 Secondary structure (protein), 1038-1039... 

Spectral Transparence Starting from 230 nm 4-Benzylphenoxy Photooxidable Groups Presence of Labile Secondary Hydrogen Atoms Photooxidation and Photoreticulation Processes - ... 

Oxidation of isopropyl alcohol (H2R) by chromic acid has been studied in det ai by Westheimer and Novick , and it was found that acetone (R) is formed nearly quantitatively. The reaction proved to be first order with respect to hydrogen chromate and second order with respect to hydrogen ions. Measurements using 2-deutero-2-propanol under identical conditions as those for the oxidation of ordinary isopropyl alcohol showed the rate of reaction to be of that with the hydrogen compound. This fact is considered to prove that the secondary hydrogen atom is removed in the rate-controlling step and that the assumption of hydride-ion abstraction can be excluded. The data are consistent with the following mechanism... 

The kinetics of secondary hydrogenation and isomerization of 1-alkenes as represented by the reaction scheme is characterized by a negative reaction order with respect to carbon monoxide.13 15... 

The results from these experiments also allowed Hannon and Traylor to determine the primary and secondary hydrogen deuterium kinetic isotope effects for the hydride abstraction reaction. If one assumes that there is no kinetic isotope effect associated with the formation of 3-deutero-l-butene, i.e. that CH2=CHCHDCH3 is formed at the same rate (k ) from both the deuterated and undeuterated substrate (Scheme 25), then one can obtain both the primary (where a deuteride ion is abstracted) and the secondary deuterium... 

Different explanations have been proposed to explain this effect, including the influence of water on the adsorbed carbon species on the surface and the reduction of secondary hydrogenation of primary olefins by water, thereby facilitating olefin readsorption and chain initiation.8... 

C. Aaserud, Model studies of secondary hydrogenation in Fischer-Tropsch synthesis studied by cobalt catalysts, Thesis, NTNU, Trondheim, 2003. 

A secondary deuterium kinetic isotope effect is observed when substitution of a deuterium atom(s) for a hydrogen atom(s) in the substrate changes the rate constant but the bond to the deuterium atom is neither broken nor formed in the transition state of the rate-determining step of the reaction. Several types of secondary hydrogen-deuterium (deuterium) KIEs are found. They are characterized by the position of the deuterium relative to the reaction centre. Thus, a secondary a-deuterium KIE is observed when an a-hydrogen(s) is replaced by deuterium [equations (1) and (2)], where L is either hydrogen or deuterium. 

Saunders also used calculations on his model reaction (54) to determine the relationship between the secondary hydrogen-deuterium (secondary hydrogen-tritium) KIEs and secondary deuterium-tritium KIEs for doubly labelled substrates and to investigate how tunnelling affects this relationship. To obtain secondary KIEs that could be checked experimentally, Saunders calculated the secondary k lk% and k lk KIEs for the hypothetical E2 reaction of a pair of doubly labelled substrates [17] and [18]. 

Table 42 The secondary hydrogen-tritium and deuterium-tritium KIEs in the E2 reactions of several arylethyltrimethylammonium bromides at 50oC. ...

Finally, tunnelling does not affect the magnitude of the experimental / significantly. Therefore, converting the experimental (in the absence of tunnelling) secondary hydrogen-tritium KIE, into the secondary... 

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