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Friedel–Crafts reaction
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<h2 id="alkylation">Alkylation</h2> <h3>With alkenes</h3> <p>In commercial applications, the alkylating agents are generally <a href="/facts/Alkene/RtYcS6kU">alkenes</a>, some of the largest scale reactions practiced in industry. Such alkylations are of major industrial importance, e.g. for the production of <a href="/facts/Ethylbenzene/aVhfY3vX">ethylbenzene</a>, the precursor to polystyrene, from benzene and ethylene and for the production of cumene from benzene and propene in <a href="/facts/Cumene_process/qG6AIc9j">cumene process</a>: </p> <p>Industrial production typically uses <a href="/facts/Solid_acid/ILa9AII5">solid acids</a> derived from a <a href="/facts/Zeolite/SNrXy4v2">zeolite</a> as the catalyst. </p> <h3>With alkyl halides</h3> <p>Friedel–Crafts alkylation involves the <a href="/facts/Alkylation/1rd5SNbt">alkylation</a> of an <a href="/facts/Aromatic_ring/wK0DzRY6">aromatic ring</a>. Traditionally, the alkylating agents are <a href="/facts/Alkyl_halide/Enb7LQqt">alkyl halides</a>. Many alkylating agents can be used instead of alkyl halides. For example, <a href="/facts/Enone/gAflh5z4">enones</a> and <a href="/facts/Epoxide/PLxRI7r1">epoxides</a> can be used in presence of protons. The reaction typically employs a strong <a href="/facts/Lewis_acid/qlLqRvg2">Lewis acid</a>, such as <a href="/facts/Aluminium_chloride/xrhvSxDr">aluminium chloride</a> as catalyst, to increase the electrophilicity of the alkylating agent.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> </p><p>This reaction suffers from the disadvantage that the product is more <a href="/facts/Nucleophile/xYccoaJQ">nucleophilic</a> than the reactant because alkyl groups are <a href="/facts/Electrophilic_aromatic_substitution/trwuWp1L">activators for the Friedel–Crafts reaction</a>. Consequently, overalkylation can occur. However, <a href="/facts/Steric_hindrance/TnX5c8HG">steric hindrance</a> can be exploited to limit the number of successive alkylation cycles that occur, as in the <i>t</i>-butylation of 1,4-dimethoxybenzene that gives only the product of two alkylation cycles and with only one of three possible isomers of it:<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> </p> <p>Furthermore, the reaction is only useful for primary alkyl halides in an intramolecular sense when a 5- or 6-membered ring is formed. For the intermolecular case, the reaction is limited to <a href="/facts/Tertiary_carbon/Don0lYjN">tertiary</a> alkylating agents, some secondary alkylating agents (ones for which carbocation rearrangement is degenerate), or alkylating agents that yield stabilized carbocations (e.g., benzylic or allylic ones). In the case of primary alkyl halides, the carbocation-like complex (R(+)---X---Al(-)Cl3) will undergo a <a href="/facts/Carbocation/vIggUxTh">carbocation</a> <a href="/facts/Rearrangement_reaction/B1XTteIJ">rearrangement reaction</a> to give almost exclusively the rearranged product derived from a secondary or tertiary carbocation.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> </p><p>Protonation of alkenes generates <a href="/facts/Carbocation/vIggUxTh">carbocations</a>, the electrophiles. A laboratory-scale example by the synthesis of <a href="/facts/Neophyl_chloride/Leesg0qU">neophyl chloride</a> from benzene and <a href="/facts/Methallyl_chloride/LKvbJCyx">methallyl chloride</a> using <a href="/facts/Sulfuric_acid/Wom6fymJ">sulfuric acid</a> catalyst.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> </p> <h4>Mechanism</h4> <p>The general mechanism for primary alkyl halides is shown in the figure below.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> </p> For primary (and possibly secondary) alkyl halides, a carbocation-like complex with the Lewis acid, [R(+)---(X---MX<i>n</i>)(–)] is more likely to be involved, rather than a free carbocation. <h3>Friedel–Crafts dealkylation</h3> <p>Friedel–Crafts alkylations can be <a href="/facts/Reversible_reaction/V3Afejgb">reversible</a>. Although this is usually undesirable it can be exploited; for instance by facilitating <a href="/facts/Transalkylation/UmAdc2UB">transalkylation</a> reactions.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p> <p>It also allows alkyl chains to be added reversibly as <a href="/facts/Protecting_group/f92hVwHl">protecting groups</a>. This approach is used industrially in the synthesis of <a href="/facts/4%2c4%2527-biphenol/sHfRktN4">4,4'-biphenol</a> via the oxidative coupling and subsequent dealkylation of <a href="/facts/2%2c6-di-tert-butylphenol/rbnjJpU2">2,6-di-tert-butylphenol</a>.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a><a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> </p> <h2 id="acylation">Acylation</h2> <p>Friedel–Crafts acylation involves the <a href="/facts/Acylation/9R8o69jN">acylation</a> of aromatic rings. Typical acylating agents are <a href="/facts/Acyl_chloride/R4ppUXre">acyl chlorides</a>. <a href="/facts/Acid_anhydride/0LvHIgAY">Acid anhydrides</a> as well as carboxylic acids are also viable. A typical <a href="/facts/Lewis_acid/qlLqRvg2">Lewis acid</a> catalyst is <a href="/facts/Aluminium_trichloride/xrhvSxDr">aluminium trichloride</a>. Because, however, the product ketone forms a rather stable complex with Lewis acids such as AlCl3, a stoichiometric amount or more of the "catalyst" must generally be employed, unlike the case of the Friedel–Crafts alkylation, in which the catalyst is constantly regenerated.<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> 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 <a href="/facts/Carbonyl/KJ71bo3X">carbonyl</a> group, the <a href="/facts/Ketone/BqQXpLo4">ketone</a> product is always less reactive than the original molecule, so multiple acylations do not occur. Also, there are no <a href="/facts/Carbocation/vIggUxTh">carbocation</a> rearrangements, as the <a href="/facts/Acylium_ion/1vRPrmUX">acylium ion</a> is stabilized by a resonance structure in which the positive charge is on the oxygen. </p> <p>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 <a href="/facts/Benzaldehyde/GyboW1KC">benzaldehyde</a> through the Friedel–Crafts pathway requires that formyl chloride be synthesized <i>in situ</i>. This is accomplished by the <a href="/facts/Gattermann-Koch_reaction/sNvenw3z">Gattermann-Koch reaction</a>, accomplished by treating benzene with <a href="/facts/Carbon_monoxide/CKuLtEMJ">carbon monoxide</a> and <a href="/facts/Hydrogen_chloride/7Wzkhomd">hydrogen chloride</a> under high pressure, catalyzed by a mixture of <a href="/facts/Aluminium_chloride/xrhvSxDr">aluminium chloride</a> and <a href="/facts/Cuprous_chloride/L8RgsAhF">cuprous chloride</a>. Simple ketones that could be obtained by Friedel–Crafts acylation are produced by alternative methods, e.g., oxidation, in industry. </p> <h3>Reaction mechanism</h3> <p>The reaction proceeds through generation of an acylium center. The reaction is completed by deprotonation of the <a href="/facts/Arenium_ion/1MsCvEX9">arenium ion</a> by AlCl4−, regenerating the AlCl3 catalyst. However, in contrast to the truly catalytic alkylation reaction, the formed ketone is a moderate Lewis base, which forms a complex with the strong Lewis acid aluminum trichloride. The formation of this complex is typically irreversible under reaction conditions. Thus, a stochiometric quantity of AlCl3 is needed. The complex is destroyed upon aqueous workup to give the desired ketone. For example, the classical synthesis of deoxybenzoin calls for 1.1 equivalents of AlCl3 with respect to the limiting reagent, phenylacetyl chloride.<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a> In certain cases, generally when the benzene ring is activated, Friedel–Crafts acylation can also be carried out with <i>catalytic</i> amounts of a milder Lewis acid (e.g. Zn(II) salts) or a Brønsted acid catalyst using the anhydride or even the carboxylic acid itself as the acylation agent. </p> <p>If desired, the resulting ketone can be subsequently reduced to the corresponding alkane substituent by either <a href="/facts/Wolff%25E2%2580%2593Kishner_reduction/5PdQQJRm">Wolff–Kishner reduction</a> or <a href="/facts/Clemmensen_reduction/h1AT6KU4">Clemmensen reduction</a>. The net result is the same as the Friedel–Crafts alkylation except that rearrangement is not possible.<a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a> </p> <h2 id="hydroxyalkylation">Hydroxyalkylation</h2> <p>Arenes react with certain <a href="/facts/Aldehyde/xSIRkW03">aldehydes</a> and ketones to form the hydroxyalkylated products, for example in the reaction of the <a href="/facts/Mesityl/4JCRbj1Y">mesityl</a> derivative of <a href="/facts/Glyoxal/e9zoq6CG">glyoxal</a> with benzene:<a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a> </p> <p>As usual, the aldehyde group is more reactive electrophile than the <a href="/facts/Phenone/ajKDIrpB">phenone</a>. </p> <h2 id="scope-and-variations">Scope and variations</h2> <p>This reaction is related to several classic named reactions: </p> <ul><li>The acylated reaction product can be converted into the alkylated product via a <a href="/facts/Clemmensen_reduction/h1AT6KU4">Clemmensen</a> or a <a href="/facts/Wolff-Kishner_reduction/5PdQQJRm">Wolff-Kishner reduction</a>.<a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a></li> <li>The <a href="/facts/Gattermann%25E2%2580%2593Koch_reaction/sNvenw3z">Gattermann–Koch reaction</a> can be used to synthesize benzaldehyde from benzene.<a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a></li> <li>The <a href="/facts/Gatterman_reaction/sNvenw3z">Gatterman reaction</a> describes arene reactions with hydrocyanic acid.<a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a><a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a></li> <li>The <a href="/facts/Houben%25E2%2580%2593Hoesch_reaction/pfYv9umk">Houben–Hoesch reaction</a> describes arene reactions with nitriles.<a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a></li> <li>A reaction modification with an aromatic phenyl ester as a reactant is called the <a href="/facts/Fries_rearrangement/7YeUle47">Fries rearrangement</a>.</li> <li>In the <a href="/facts/Scholl_reaction/UaYDPAKr">Scholl reaction</a> two arenes couple directly (sometimes called Friedel–Crafts arylation).<a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a></li> <li>In the <a href="/facts/Blanc_chloromethylation/wAzbsUMc">Blanc chloromethylation</a> a chloromethyl group is added to an arene with formaldehyde, hydrochloric acid and zinc chloride.</li> <li>The Bogert–Cook synthesis (1933) involves the <a href="/facts/Dehydration_reaction/dTAxlyRX">dehydration</a> and <a href="/facts/Isomerization/sxv23uKl">isomerization</a> of <i>1-β-phenylethylcyclohexanol</i> to the octahydro derivative of <a href="/facts/Phenanthrene/tE9YALIM">phenanthrene</a><a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a></li></ul> <ul><li>The Darzens–Nenitzescu synthesis of ketones (1910, 1936) involves the acylation of <a href="/facts/Cyclohexene/EWIV90Fx">cyclohexene</a> with <a href="/facts/Acetyl_chloride/SU9Bq4tG">acetyl chloride</a> to methylcyclohexenylketone.</li> <li>In the related Nenitzescu reductive acylation (1936) a <a href="/facts/Saturated_and_unsaturated_compounds/tde2C216">saturated</a> <a href="/facts/Hydrocarbon/Dcg95Ju5">hydrocarbon</a> is added making it a reductive acylation to methylcyclohexylketone</li> <li>The Nencki reaction (1881) is the ring acetylation of phenols with acids in the presence of zinc chloride.<a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a></li> <li>In a <a href="/facts/Green_chemistry/7csVY28w">green chemistry</a> variation <a href="/facts/Aluminium_chloride/xrhvSxDr">aluminium chloride</a> is replaced by <a href="/facts/Graphite/sSf3KMXr">graphite</a> in an alkylation of <a href="/facts/P-Xylene/PUyGrJSe"><i>p</i>-xylene</a> with <a href="/facts/2-bromobutane/H07AJfMY">2-bromobutane</a>. This variation will not work with primary halides from which less carbocation involvement is inferred.<a class="footnote-ref" id="fnref:26" href="#fn:26"><sup>26</sup></a></li></ul> <h3>Dyes</h3> <p>Friedel–Crafts reactions have been used in the synthesis of several <a href="/facts/Triphenylmethane/35o8VWeP">triarylmethane</a> and <a href="/facts/Xanthene/Dd1jDgBu">xanthene</a> <a href="/facts/Dye/a1NSlcsG">dyes</a>.<a class="footnote-ref" id="fnref:27" href="#fn:27"><sup>27</sup></a> Examples are the synthesis of <a href="/facts/Thymolphthalein/hk6I5PGN">thymolphthalein</a> (a pH indicator) from two equivalents of <a href="/facts/Thymol/S6u6qWcL">thymol</a> and <a href="/facts/Phthalic_anhydride/0naPEKVt">phthalic anhydride</a>: </p> <p>A reaction of phthalic anhydride with <a href="/facts/Resorcinol/fI1glr61">resorcinol</a> in the presence of <a href="/facts/Zinc_chloride/aYscGQL7">zinc chloride</a> gives the fluorophore <a href="/facts/Fluorescein/8E4xH5at">fluorescein</a>. Replacing resorcinol by N,N-diethylaminophenol in this reaction gives <a href="/facts/Rhodamine_B/cy4pVE9C">rhodamine B</a>: </p> <h3>Haworth synthesis</h3> <p>The <a href="/facts/Haworth_synthesis/WX0wSWJ0">Haworth synthesis</a> is a classic method for the synthesis of polycyclic aromatic hydrocarbons. In this reaction, an <a href="/facts/Arene_(disambiguation)/S5lpGPsm">arene</a> is reacted with <a href="/facts/Succinic_anhydride/uwQwM00N">succinic anhydride</a>, the subsequent product is then reduced in either a <a href="/facts/Clemmensen_reduction/h1AT6KU4">Clemmensen reduction</a> or a <a href="/facts/Wolff%25E2%2580%2593Kishner_reduction/5PdQQJRm">Wolff-Kishner reduction</a>. Lastly, a second Friedel-Crafts acylation takes place with addition of acid.<a class="footnote-ref" id="fnref:28" href="#fn:28"><sup>28</sup></a> </p> <p>The product formed in this reaction is then analogously reduced, followed by a dehydrogenation reaction (with the reagent <a href="/facts/Selenium_dioxide/naIqT939">SeO2</a> for example) to extend the aromatic ring system.<a class="footnote-ref" id="fnref:29" href="#fn:29"><sup>29</sup></a> </p> <h3>Friedel–Crafts test for aromatic hydrocarbons</h3> <p>Reaction of <a href="/facts/Chloroform/gvzuJMXa">chloroform</a> with aromatic compounds using an <a href="/facts/Aluminium_chloride/xrhvSxDr">aluminium chloride</a> catalyst gives triarylmethanes, which are often brightly colored, as is the case in triarylmethane dyes. This is a bench test for aromatic compounds.<a class="footnote-ref" id="fnref:30" href="#fn:30"><sup>30</sup></a> </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Friedel_family/NgfmRKjv">Friedel family</a>, lineage of French scientists</li> <li><a href="/facts/Hydrodealkylation/bmjnAsSq">Hydrodealkylation</a></li> <li><a href="/facts/Transalkylation/UmAdc2UB">Transalkylation</a></li></ul> <h3>Friedel–Crafts reactions published on <i>Organic Syntheses</i></h3> <ul><li>Alkylations: <ul><li>Everett M. Schultz; Sally Mickey (1949). <a href="http://www.orgsyn.org/Content/pdfs/procedures/CV3P0343.pdf">"Diphenylacetone"</a> (PDF). <i><a href="/facts/Organic_Syntheses/WLFePEzH">Organic Syntheses</a></i>. 29: 38.</li> <li>Lee Irvin Smith (1930). <a href="http://www.orgsyn.org/Content/pdfs/procedures/CV2P0248.pdf">"Durene"</a> (PDF). <i><a href="/facts/Organic_Syntheses/WLFePEzH">Organic Syntheses</a></i>. 10: 32.</li> <li>C. S. Marvel; W. M. Sperry (1928). <a href="http://www.orgsyn.org/Content/pdfs/procedures/CV1P0095.pdf">"Benzophenone"</a> (PDF). <i><a href="/facts/Organic_Syntheses/WLFePEzH">Organic Syntheses</a></i>. 8: 26.</li></ul></li> <li>Acylations: <ul><li>R. E. Lutz (1940). <a href="http://www.orgsyn.org/Content/pdfs/procedures/CV3P0248.pdf">"trans-dienzoethylene"</a> (PDF). <i><a href="/facts/Organic_Syntheses/WLFePEzH">Organic Syntheses</a></i>. 20: 29.</li> <li>L. F. Fieser (1940). <a href="http://www.orgsyn.org/Content/pdfs/procedures/CV3P0006.pdf">"β-(3-Acenaphthoyl)Propionic acid"</a> (PDF). <i><a href="/facts/Organic_Syntheses/WLFePEzH">Organic Syntheses</a></i>. 20: 1.</li> <li>C. F. H. Allen; W. E. Barker (1932). <a href="http://www.orgsyn.org/Content/pdfs/procedures/CV2P0156.pdf">"Desoxybenzoin"</a> (PDF). <i><a href="/facts/Organic_Syntheses/WLFePEzH">Organic Syntheses</a></i>. 12: 16.</li> <li>Kamil Paruch; Libor Vyklicky; Thomas J. Katz (2003). <a href="http://www.orgsyn.org/Content/pdfs/procedures/v80p0227.pdf">"Preparation of 9,10-dimethoxyphenanthrene and 3,6-diacetyl-9,10-dimethoxyphenanthrene"</a> (PDF). <i><a href="/facts/Organic_Syntheses/WLFePEzH">Organic Syntheses</a></i>. 80: 227.</li> <li>Roger Adams; C. R. Noller (1925). <a href="http://www.orgsyn.org/Content/pdfs/procedures/CV1P0109.pdf">"p-bromoacetophenone"</a> (PDF). <i><a href="/facts/Organic_Syntheses/WLFePEzH">Organic Syntheses</a></i>. 5: 17.</li> <li>L. F. Fieser (1925). <a href="http://www.orgsyn.org/Content/pdfs/procedures/CV1P0353.pdf">"β-methyanthraquinone"</a> (PDF). <i><a href="/facts/Organic_Syntheses/WLFePEzH">Organic Syntheses</a></i>. 4: 43.</li> <li>Perry C. Reeves (1977). <a href="http://www.orgsyn.org/Content/pdfs/procedures/CV6P0625.pdf">"Carboxylation of aromatic compounds: ferrocenecarboxylic acid"</a> (PDF). <i><a href="/facts/Organic_Syntheses/WLFePEzH">Organic Syntheses</a></i>. 56: 28.</li></ul></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Friedel, C.; Crafts, J. M. (1877) "Sur une nouvelle méthode générale de synthèse d'hydrocarbures, d'acétones, etc.," Compt. Rend., 84: 1392 & 1450. <a href="http://gallica.bnf.fr/ark:/12148/bpt6k30410/f1386.table" target="_blank">http://gallica.bnf.fr/ark:/12148/bpt6k30410/f1386.table</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>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. {{cite journal}}: ISBN / Date incompatibility (help) <a href="0471264180" target="_blank">0471264180</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Groves, J. K. (1972). "The Friedel–Crafts acylation of alkenes". Chem. Soc. Rev. 1: 73. doi:10.1039/cs9720100073. <a href="/wiki/Chem._Soc._Rev." target="_blank">/wiki/Chem._Soc._Rev.</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Eyley, S. C. (1991). "The Aliphatic Friedel–Crafts Reaction". Compr. Org. Synth. 2: 707–731. doi:10.1016/B978-0-08-052349-1.00045-7. ISBN 978-0-08-052349-1. <a href="978-0-08-052349-1" target="_blank">978-0-08-052349-1</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Heaney, H. (1991). "The Bimolecular Aromatic Friedel–Crafts Reaction". Compr. Org. Synth. 2: 733–752. doi:10.1016/B978-0-08-052349-1.00046-9. ISBN 978-0-08-052349-1. <a href="978-0-08-052349-1" target="_blank">978-0-08-052349-1</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Rueping, M.; Nachtsheim, B. J. (2010). "A review of new developments in the Friedel–Crafts alkylation – From green chemistry to asymmetric catalysis". Beilstein J. Org. Chem. 6 (6): 6. doi:10.3762/bjoc.6.6. PMC 2870981. PMID 20485588. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2870981" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2870981</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>L., Williamson, Kenneth (4 January 2016). Macroscale and microscale organic experiments. Masters, Katherine M. (Seventh ed.). Boston, MA, USA. ISBN 9781305577190. OCLC 915490547.{{cite book}}: CS1 maint: location missing publisher (link) CS1 maint: multiple names: authors list (link) <a href="9781305577190" target="_blank">9781305577190</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Smith, Michael B.; March, Jerry (2007), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (6th ed.), New York: Wiley-Interscience, ISBN 978-0-471-72091-1 <a href="978-0-471-72091-1" target="_blank">978-0-471-72091-1</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Smith, W. T. Jr.; Sellas, J. T. (1952). "Neophyl Chloride". Organic Syntheses. 32: 90. doi:10.15227/orgsyn.032.0090. <a href="/wiki/Organic_Syntheses" target="_blank">/wiki/Organic_Syntheses</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Smith, Michael B.; March, Jerry (2007), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (6th ed.), New York: Wiley-Interscience, ISBN 978-0-471-72091-1 <a href="978-0-471-72091-1" target="_blank">978-0-471-72091-1</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Tsai, Tseng-Chang "Disproportionation and Transalkylation of Alkylbenzenes over Zeolite Catalysts". Elsevier Science, 1999 <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Helmut Fiege; Heinz-Werner Voges; Toshikazu Hamamoto; et al. (2002). "Phenol Derivatives". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a19_313. ISBN 3527306730. <a href="3527306730" target="_blank">3527306730</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>Hay, Allan S. (1969). "p,p'-Biphenols". The Journal of Organic Chemistry. 34 (4): 1160–1161. doi:10.1021/jo01256a098. <a href="/wiki/The_Journal_of_Organic_Chemistry" target="_blank">/wiki/The_Journal_of_Organic_Chemistry</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>Somerville, L. F.; Allen, C. F. H. (1933). "β-Benzoylpropionic acid". Organic Syntheses. 13: 12. doi:10.15227/orgsyn.013.0012. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>"Desoxybenzoin". orgsyn.org. 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