Friedel -- Crafts reaction - wikipedia Friedel -- Crafts reaction Friedel - Crafts reaction Named after Charles Friedel James Crafts Reaction type Coupling reaction Identifiers RSC ontology ID RXNO : 0000369 The Friedel -- Crafts reactions are a set of reactions developed by Charles Friedel and James Crafts in 1877 to attach substituents to an aromatic ring. Friedel -- Crafts reactions are of two main types : alkylation reactions and acylation reactions. Both proceed by electrophilic aromatic substitution. Contents 1 Friedel -- Crafts alkylation 2 Friedel -- Crafts dealkylation 3 Friedel -- Crafts acylation 3.1 Reaction mechanism 4 Friedel -- Crafts hydroxyalkylation 5 Friedel -- Crafts sulfonylation 6 Scope and variations 6.1 Dyes 6.2 Haworth reactions 6.3 Friedel -- Crafts test for aromatic hydrocarbons 7 See also 8 References 8.1 Friedel -- Crafts reactions published on Organic Syntheses Friedel -- Crafts alkylation Friedel - Crafts alkylation Named after Charles Friedel James Crafts Reaction type Coupling reaction Identifiers Organic Chemistry Portal friedel - crafts - alkylation RSC ontology ID RXNO : 0000046 Friedel -- Crafts alkylation involves the alkylation of an aromatic ring with an alkyl halide using a strong Lewis acid catalyst. With anhydrous ferric chloride as a catalyst, the alkyl group attaches at the former site of the chloride ion. The general mechanism is shown below. This reaction suffers from the disadvantage that the product is more nucleophilic than the reactant. Consequenly, overalkylation occurs. Furthermore, the reaction is only very useful for tertiary carbon and secondary alkylating agents. Otherwise the incipient carbocation ( R ) will undergo a carbocation rearrangement reaction. Steric hindrance can be exploited to limit the number of alkylations, as in the t - butylation of 1, 4 - dimethoxybenzene. Alkylations are not limited to alkyl halides : Friedel -- Crafts reactions are possible with any carbocationic intermediate such as those derived from alkenes and a protic acid, Lewis acid, enones, and epoxides. An example is the synthesis of neophyl chloride from benzene and methallyl chloride : H C = C ( CH ) CH Cl + C H → C H C ( CH ) CH Cl In one study the electrophile is a bromonium ion derived from an alkene and NBS : In this reaction samarium ( III ) triflate is believed to activate the NBS halogen donor in halonium ion formation. Friedel -- Crafts dealkylation Friedel -- Crafts alkylation has been hypothesized to be reversible. In a reversed Friedel -- Crafts reaction or Friedel -- Crafts dealkylation, alkyl groups are removed in the presence of protons or other Lewis acid. For example, in a multiple addition of ethyl bromide to benzene, ortho and para substitution is expected after the first monosubstitution step because an alkyl group is an activating group. However, the actual reaction product is 1, 3, 5 - triethylbenzene with all alkyl groups as a meta substituent. Thermodynamic reaction control makes sure that thermodynamically favored meta substitution with steric hindrance minimized takes prevalence over less favorable ortho and para substitution by chemical equilibration. The ultimate reaction product is thus the result of a series of alkylations and dealkylations. Friedel -- Crafts acylation Friedel - Crafts acylation Named after Charles Friedel James Crafts Reaction type Coupling reaction Identifiers Organic Chemistry Portal friedel - crafts - acylation RSC ontology ID RXNO : 0000045 Friedel -- Crafts acylation involves the acylation of aromatic rings. Typical acylating agents are acyl chlorides. Typical Lewis acid catalysts are acids and aluminium trichloride... Friedel -- Crafts acylation is also possible with acid anhydrides. Reaction conditions are similar to the Friedel -- Crafts alkylation. This reaction has several advantages over the alkylation reaction. Due to the electron - withdrawing effect of the carbonyl group, the ketone product is always less reactive than the original molecule, so multiple acylations do not occur. Also, there are no carbocation rearrangements, as the carbonium ion is stabilized by a resonance structure in which the positive charge is on the oxygen. The viability of the Friedel -- Crafts acylation depends on the stability of the acyl chloride reagent. Formyl chloride, for example, is too unstable to be isolated. Thus, synthesis of benzaldehyde via the Friedel -- Crafts pathway requires that formyl chloride be synthesized in situ. This is accomplished via the Gattermann - Koch reaction, accomplished by treating benzene with carbon monoxide and hydrogen chloride under high pressure, catalyzed by a mixture of aluminium chloride and cuprous chloride. Reaction mechanism The reaction proceeds via generation of an acylium center : The reaction is completed by deprotonation of the arenium ion by AlCl, regenerating the AlCl catalyst : If desired, the resulting ketone can be subsequently reduced to the corresponding alkane substituent by either Wolff -- Kishner reduction or Clemmensen reduction. The net result is the same as the Friedel -- Crafts alkylation except that rearrangement is not possible. Friedel -- Crafts hydroxyalkylation Arenes react with certain aldehydes and ketones to form the hydroxyalkylated product for example in the reaction of the mesityl derivative of glyoxal with benzene to form a benzoin with an alcohol rather than a carbonyl group : Friedel -- Crafts sulfonylation Under Friedel -- Crafts reaction conditions, arenes react with sulfonyl halides and sulfonic acid anhydrides affording sulfones. Commonly used catalysts include AlCl, FeCl, GaCl, BF, SbCl, BiCl and Bi ( OTf ), among others. Intramolecular Friedel -- Crafts cyclization occurs with 2 - phenyl - 1 - ethanesulfonyl chloride, 3 - phenyl - 1 - propanesulfonyl chloride and 4 - phenyl - 1 - butanesulfonyl chloride on heating in nitrobenzene with AlCl. Sulfenyl and sulfinyl chlorides also undergo Friedel -- Crafts -- type reactions, affording sulfides and sulfoxides, respectively. Both aryl sulfinyl chlorides and diaryl sulfoxides can be prepared from arenes through reaction with thionyl chloride in the presence of catalysts such as BiCl, Bi ( OTf ), LiClO or NaClO. Scope and variations This reaction is related to several classic named reactions : The acylated reaction product can be converted into the alkylated product via a Clemmensen reduction. The Gattermann -- Koch reaction can be used to synthesize benzaldehyde from benzene. The Gatterman reaction describes arene reactions with hydrocyanic acid. The Houben -- Hoesch reaction describes arene reactions with nitriles. A reaction modification with an aromatic phenyl ester as a reactant is called the Fries rearrangement. In the Scholl reaction two arenes couple directly ( sometimes called Friedel -- Crafts arylation ). In the Zincke -- Suhl reaction p - cresol is alkylated to a cyclohexadienone with tetrachloromethane. In the Blanc chloromethylation a chloromethyl group is added to an arene with formaldehyde, hydrochloric acid and zinc chloride. The Bogert -- Cook synthesis ( 1933 ) involves the dehydration and isomerization of 1 - β - phenylethylcyclohexanol to the octahydro derivative of phenanthrene The Darzens -- Nenitzescu synthesis of ketones ( 1910, 1936 ) involves the acylation of cyclohexene with acetyl chloride to methylcyclohexenylketone. In the related Nenitzescu reductive acylation ( 1936 ) a saturated hydrocarbon is added making it a reductive acylation to methylcyclohexylketone The Nencki reaction ( 1881 ) is the ring acetylation of phenols with acids in the presence of zinc chloride. In a green chemistry variation aluminium chloride is replaced by graphite in an alkylation of p - xylene with 2 - bromobutane. This variation will not work with primary halides from which less carbocation involvement is inferred. Dyes Friedel -- Crafts reactions have been used in the synthesis of several triarylmethane and xanthene dyes. Examples are the synthesis of thymolphthalein ( a pH indicator ) from two equivalents of thymol and phthalic anhydride : A reaction of phthalic anhydride with resorcinol in the presence of zinc chloride gives the fluorophore Fluorescein. Replacing resorcinol by N, N - diethylaminophenol in this reaction gives rhodamine B : Haworth reactions The Haworth reaction is a classic method for the synthesis of 1 - tetralone. In it benzene is reacted with succinic anhydride, the intermediate product is reduced and a second FC acylation takes place with addition of acid. In a related reaction, phenanthrene is synthesized from naphthalene and succinic anhydride in a series of steps. Friedel -- Crafts test for aromatic hydrocarbons Reaction of chloroform with aromatic compounds using an aluminium chloride catalyst gives triarylmethanes, which are often brightly colored, as is the case in triarylmethane dyes. This is a bench test for aromatic compounds. See also Ethylene oxide Friedel family, a rich lineage of French scientists Hydrodealkylation Transalkylation References Jump up ^ Friedel, C. ; Crafts, J.M. ( 1877 ) `` Sur une nouvelle méthode générale de synthèse d'hydrocarbures, d'acétones, etc., '' Compt. Rend., 84 : 1392 & 1450. Jump up ^ Price, C.C. ( 1946 ). `` The Alkylation of Aromatic Compounds by the Friedel - Crafts Method ''. Org. React. 3 : 1. doi : 10.1002 / 0471264180. or003. 01. ISBN 0471264180. Jump up ^ Groves, J.K. ( 1972 ). `` The Friedel -- Crafts acylation of alkenes ''. Chem. Soc. Rev. 1 : 73. doi : 10.1039 / cs9720100073. Jump up ^ Eyley, S.C. ( 1991 ). `` The Aliphatic Friedel -- Crafts Reaction ''. Comp. Org. 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Maselli ( 1898 ) `` Su alcuni derivati clorurati de trossimetilene '' ( On some chlorinated derivatives of 1, 3, 5 - trioxane ), Gazzetta Chimica Italiana, 28 ( part 2 ) : 477 - 500 ; see especially p. 495. Jump up ^ This reaction with phosphorus pentoxide : Kamp, J.V.D. ; Mosettig, E. ( 1936 ). `` Trans - and Cis - As - Octahydrophenanthrene ''. Journal of the American Chemical Society. 58 ( 6 ) : 1062 -- 1063. doi : 10.1021 / ja01297a514. Jump up ^ Nencki, M. ; Sieber, N. ( 1881 ). `` Ueber die Verbindungen der ein - und zweibasischen Fettsäuren mit Phenolen ''. J. Prakt. Chem. ( in German ). 23 : 147 -- 156. doi : 10.1002 / prac. 18810230111. Jump up ^ Sereda, Grigoriy A. ; Rajpara, Vikul B. ( 2007 ). `` A Green Alternative to Aluminum Chloride Alkylation of Xylene ''. J. Chem. Educ. 2007 ( 84 ) : 692. Bibcode : 2007JChEd... 84... 692S. doi : 10.1021 / ed084p692. Jump up ^ McCullagh, James V. ; Daggett, Kelly A. ( 2007 ). `` Synthesis of Triarylmethane and Xanthene Dyes Using Electrophilic Aromatic Substitution Reactions ''. J. Chem. Educ. 84 : 1799. doi : 10.1021 / ed084p1799. Jump up ^ Haworth, Robert Downs ( 1932 ). `` Syntheses of alkylphenanthrenes. Part I. 1 -, 2 -, 3 -, and 4 - Methylphenanthrenes ''. J. Chem. Soc. : 1125. doi : 10.1039 / JR9320001125. Jump up ^ Li, Jie Jack ( 2003 ) Name Reactions : A Collection of Detailed Reaction Mechanisms, Springer, ISBN 3 - 540 - 40203 - 9, p. 175. Jump up ^ John C. Gilbert., Stephen F. Martin. Experimental Organic Chemistry : A Miniscale and Microscale Approach. Brooks / Cole CENGAGE Learning, 2011. pp 872. 25.10 Aromatic Hydrocarbons and Aryl Halides - Classification test. ISBN 978 - 1 - 4390 - 4914 - 3 Friedel -- Crafts reactions published on Organic Syntheses Alkylations : Diphenylacetone, Organic Syntheses, Coll. Vol. 3, p. 343 ( 1955 ) ; Vol. 29, p. 38 ( 1949 ) Article link. Reaction of p - xylene with chloromethane to durene Organic Syntheses, Coll. Vol. 2, p. 248 ( 1943 ) ; Vol. 10, p. 32 ( 1930 ). Article link Synthesis of benzophenone from benzene and tetrachloromethane Organic Syntheses, Coll. Vol. 1, p. 95 ( 1941 ) ; Vol. 8, p. 26 ( 1928 ). Article link Acylations : Dibenzoylethylene Organic Syntheses, Coll. Vol. 3, p. 248 ( 1955 ) ; Vol. 20, p. 29 ( 1940 ) Article link. reaction of acenaphthene plus succinic acid Organic Syntheses, Coll. Vol. 3, p. 6 ( 1955 ) ; Vol. 20, p. 1 ( 1940 ). Article link Desoxybenzoin Organic Syntheses, Coll. Vol. 2, p. 156 ( 1943 ) ; Vol. 12, p. 16 ( 1932 ). Article link Acylation of a phenanthrene compound Organic Syntheses, Vol. 80, p. 227 Link Reaction of bromobenzene with acetic anhydride Organic Syntheses, Coll. Vol. 1, p. 109 ( 1941 ) ; Vol. 5, p. 17 ( 1925 ). Article link beta - methylanthraquinone, Organic Syntheses, Coll. Vol. 1, p. 353 ( 1941 ) ; Vol. 4, p. 43 ( 1925 ). Article link Benzoylation of ferrocene Organic Syntheses, Coll. Vol. 6, p. 625 ( 1988 ) ; Vol. 56, p. 28 ( 1977 ). Article link NDL : 00562092 Retrieved from `` https://en.wikipedia.org/w/index.php?title=Friedel -- Crafts_reaction&oldid = 842291412 '' Categories : Coupling reactions Substitution reactions Carbon - carbon bond forming reactions Name reactions Hidden categories : CS1 maint : Multiple names : authors list Pages with citations lacking titles CS1 German - language sources ( de ) All articles with dead external links Articles with dead external links from December 2017 Articles with permanently dead external links Use dmy dates from May 2013 All articles with unsourced statements Articles with unsourced statements from December 2011 Articles with unsourced statements from June 2017 Talk Contents About Wikipedia Català Dansk Deutsch Eesti Ελληνικά Español فارسی Français हिन्दी Bahasa Indonesia Italiano עברית Magyar Nederlands 日本 語 Norsk Polski Português Română Русский Slovenščina Српски / srpski Srpskohrvatski / српскохрватски Suomi Svenska தமிழ் Українська 中文 20 more Edit links This page was last edited on 21 May 2018, at 14 : 16. 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Question: in the friedel crafts acylation reaction aluminum chloride functions as a
Answer: catalyst