Friedel-Crafts reactions are the electorophilic reactions catalyzed by Lewis acid type acidic halides or proton acids. They require a reactant-catalyst complex which can interact with either π-or δ-donor type subutrates.The electrophilic complex is either polarized or ionic type. There is no difference in principle between reactions of π- and δ-donor systems, but the π-bonds generally react more readily. Reaction of the electorophilic complex with the substrate results in the formation of an intermediate δ-complex, which determines the reaction rate. Electrophilic aromatic substitutions involving strongly electrophilic reagents show low substrate selectivity, but high positional selectivity. This suggests that the transition state lies early on the reaction coordinate, resembling π-complex. In reactions with weak electrophiles, it lies late, resembling intermediate δ-complex.
In relation to Friedel-Crafts acylation, complexes of (ArH·MX3), (ArH·HX·MX3), and (RCOX·MX3) were chronologically reviewed on their structual formulations up to date. Properties of their complexes and their roles in the reaction were explained in terms of their differences between π-and σ-type structure. The X-ray crystal analytical results were quoted to make clear the structual small changes between π-axial and π-edgewize complexes and between ionic and nonionic complexes of (RCOX·MX3), and also to demonstrate the characteristics of σ-complex. From the recent results obtained in nonconventional attack at ipso position, some comment was added about the difficulty of finding structual relationship between intermediate complexes and products.
The contents of this article are as follows; (1) An introduction and some catalysts which can be used in Friedel-Crafts reaction instead of AlCl3 and at the same time have the merit only a catalytic amount is enough to perform the reaction. Three kinds of this catalyst are (i) ZSM-5 catalyst of Mobil Oil Co, (ii) Fe2 (SO4) 3 and (iii) CF3 SO3H. (2) Some new Friedel-Crafts reactions in aromatic compounds. (3) Some new Friedel-Crafts reactions in aliphatic compounds.
Reactions of olefins with various electrophilic reagents are classified into six types written below and each is discussed briefly. In particular, trifluoro-and trichloroacetylation of vinyl ethers, N-vinylsulfonamides, N-vinylcarboxmides and vinyl sulfides are compared with Friedel-Crafts acylations of aromatic compounds and discussed from mechanistic standpoint of view. The six types are as follows; i) addition reactions forming definite addition products, ii) addition reactions to give mixtures of isomerized and/or polymerized materials, iii) the so-called addition-elimination reactions to give substitution products, iv) reactions giving stable cations (e. g., iminium salts in the case of acylation of enamines), v) substitution reactions involving rate-determining formation of carbenium intermediates followed by rapid deprotonation (e. g., acylation of vinyl ethers) and vi) substitution reactions occurring with one-step process (e. g., acylation of vinyl sulfides).
A new general process has been developed for specific ortho hydroxybenzylation of secondary anilines and specific ortho acylation of anilines using anilinodichloroboranes. The distinctive exchange of the reaction site of anilines in the presence of boron trichloride instead of other electrophilic metal halide is very noteworthy. The mechanistic hypothesis, scope and limitations and application are described.
Biomimetic cyclization reactions of acyclic isoprenoids and their derivatives were surveyed, following the classification, 1) those starting at the head part of acyclic precursor and simulating higher terpenoid biosynthesis, 2) those activated at the tail part and imitating lower terpenoid biogenesis. The application of these reactions to the synthesis of some natural products was also reviewed.
Various oxides themselves and mixed oxides are known as a solid acid catalyst, and they catalyze many useful reactions in the field of not only organic synthetic chemistry but petrochemical industry, such as cracking, alkylation, isomerization and hydration. A solid acid is characterized by its acid strength and acidity, and these two factors essentially influence on the catalytic activities and selectivities. In this review, general properties of solid acid catalyst and determination methods of solid acid strength and acidity are described. And some typical reactions catalyzed by solid acids are reviewed.
Industrial applications of the liquid phase Friedel-Crafts Alkylation using Aluminum Chloride as eatalyst are reviewed, especially focusing on the manufacture of ethylbenzene and cumene. Recent advances in industrial processes and some of the experimental data concerning catalyst deactivation are discussed.
The present review is concerned with the manufactures of the dodecylbenzens. The terms dodecylbenzene and detergent alkylate are synonymously used in the detergent industry. Dodecylbenzene is the product prepared by alkylation of benzene with propylenetetramers, n-olefins, α-olefins or alkyl chlorides, and is a mixture of isomeric monoalkyl benzenes. Alkylation is a typical Friedel-Craft type reaction using HF and AlCl3 as catalysts.
Alkylation processes for the production of gasolines were reviewed, and recent advances in mechanisms of the alkylation reaction were described. Acid-soluble hydrocarbons including alkylsulfates play an important role as intermediates in isobutane/olefin alkylation reaction over H2SO4. Reactions of olefins with H2SO4 produce acid-soluble, large cations such as i-C+12, i-C+16etc., which decompose to afford DMH and light ends such as C5-C7 isoparaffins. The detailed mechanisms of the overall alkylations, however, are still remained to be investigated. Approaches to utilize solid catalysts such as solid superacids and zeolites insteed of liquid H2SO4and HF in the isobutane/olefin alkylation were briefly discussed. No such process is in operation as the fixed-bed alkylation employing solid catalysts. Nonetheless not a few patents on this aspect of alkylation are seen. Finally, the recent advent of a new class of shape-selective zeolites which catalyse methanol to gasoline conversion was also described.
Butyl rubber is produced by copolymerizing isobutylene with small amounts of isoprene. In 1937, R. E. Thomas and W. J. Sparks at the Exxon Research and Engineering Co. suceeded in introducing unsaturation by incorporating a few isoprene units into the copolymer thereby making it vulcanizable. The first commercial scale butyl rubber plant in Baton Rouge was on stream in 1943. Eight butyl rubber plants, to which Esso process was originally applied, are now running in the world with about 450 KT/Y capaicty excluding east side party. The items described in this report are as follows : 1. Historical background of butyl rubber development and commercialization 2. Present butyl rubber plant location, production capacity, plant completion year, etc. 3. Butyl rubber types, specifications, and their applications 4. Polymerization chemistry and molecular structure of butyl and halobutyl polymer 5. Butyl/halobutyl rubber manufacturing process
The petroleum resins comprise a class of synthetic polymeric hydrocarbon products derived from a variable mixture of unsaturated monomers obtained as volatile by-products, mainly C5 and C9 fractions, in the cracking of natural gas or petroleum naphthas. Petroleum resins are produced by polymerizing cationically by Friedel-Crafts catalysts. In the world, the production capacity of petroleum resins is now about 630, 000 tonnes/year, and that the petroleum resins have rapidly become the resin of choise in any areas-paints, printing inks, rubber compounds and adhesives. Petroleum resins can still be regarded as new materials-they are capable of wide development and refinement with close tailoring of properties to meet the need of any application. This review will refer to the present state of petroleum resin industry-various raw materials, polymerization conditions, catalysts, catalyst removals and modification of petroleum resins.