有机化学 有机化学. 一种用于从和乙烯中单步制造烯的催化剂

Unlike the easy catalytic hydrogenation of an alkene double bond, hydrogenation of a benzene double bond under similar reaction conditions does not take place easily. For example, in the reduction of stilbene, the benzene ring remains unaffected while the alkene bond gets reduced. Hydrogenation of an alkene double bond is exothermic and a favorable process. In contrast, to hydrogenate the first unsaturated bond of benzene, an energy input is needed; that is, the process is endothermic. This is...

Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...

Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.

Chlorination and bromination are important classes of electrophilic aromatic substitutions, where benzene reacts with chlorine or bromine in the presence of a Lewis acid catalyst to give halogenated substitution products. A Lewis acid such as aluminium chloride or ferric chloride catalyzes the chlorination, and ferric bromide catalyzes the bromination reactions. During the bromination of alkenes, bromine polarizes and becomes electrophilic. However, in the bromination of benzene, the bromine...

Birch reduction uses solvated electrons as reducing agents. The reaction converts benzene to 1,4-cyclohexadiene. The reaction proceeds by the transfer of a single electron to the ring to form a benzene radical anion. This anion is highly basic—it abstracts a proton from the alcohol to form a cyclohexadienyl radical. Another single electron transfer gives the cyclohexadienyl anion. A proton transfer from the alcohol forms 1,4-cyclohexadiene. Since this reduction occurs via radical anion...

Benzylic halogenation takes place under conditions that favor radical reactions such as heat, light, or a free radical initiator like peroxide.