), Virtual Textbook of Organic Chemistry. Question: In A Clemmensen Reduction, An Aryl Ketone Is Reduced To An Oaryl Aldehyde Caryl Alkane Aryl Carboxylic Acid Aryl Ester Aryi Anhydride Identify The Electrophile For The Friedel-Crafts Acylation Of Benzene. Unless otherwise noted, LibreTexts content is licensed by CC BY-NC-SA 3.0. … * In Clemmensen reduction, the amalgamated zinc in HCl is used as reducing agent. Clemmensen reduction is complementary to Wolff-Kishner reduction, which also converts aldehydes and ketones to hydrocarbons, in that the former is carried out in strongly acidic conditions and the latter in strongly basic conditions.

After a critical review, we present a complete and coherent reaction mechanism that involves the formation of a free carbene as well as a zinc carbene and two different carbanionic species as intermediates. This reaction is named after Erik Christian Clemmensen, a Danish chemist. 4) But the phenol group is not affected in Clemmensen reduction. It is the reduction of carbonyl groups ( in aldehyde and ketone) to methylene group. * The Clemmensen reduction is complementary to Wolff-Kishner reduction, which may be used to reduce acid sensitive compounds. The Wolff–Kishner reduction is a reaction used in organic chemistry to convert carbonyl functionalities into methylene groups.In the context of complex molecule synthesis, it is most frequently employed to remove a carbonyl group after it has served its synthetic purpose of … * In Clemmensen reduction, the amalgamated zinc in HCl is used as reducing agent.

The mechanism of Clemmensen reduction is not fully understood; intermediacy of radicals are implicated. Clemmensen reduction is a chemical reaction described as a reduction of ketones (or aldehydes) to alkanes using zinc amalgam and concentrated hydrochloric acid. This reaction done with zinc amalgam and hydrochloric acid and it is generally known as Clemmensen reduction. Uncontrolled deuteration has been achieved from diosgenin, whereas [16,16,22,22,23,23-(2)H(6)]-(25R)-26-hydroxycholesterol (1) can be synthesized from kryptogenin. With aliphatic or cyclic ketones, modified Clemmensen conditions using activated zinc dust in an anhydrous solution of hydrogen chloride in diethyl ether or acetic anhydride is much more effective.[7]. to alkanes. In spite of the antiquity of this reaction, the mechanism of the Clemmensen reduction remains obscure. The mercury alloyed with the zinc does not participate in the reaction, it serves only to provide a clean active metal surface. However, the corresponding alcohol is believed not to be an intermediate, since subjection of the alcohol to Clemmensen conditions generally does not afford the alkane product. However Have questions or comments? The Clemmensen reduction may be fine for the laboratory, but fundamentally many industries wouldn't use it due to scaling up the use of mercury. * The Clemmensen reduction occurs over the surface of zinc catalyst. Prof. Steven Farmer (Sonoma State University), William Reusch, Professor Emeritus (Michigan State U. )", "Modified Clemmensen Reduction: Cholestane", https://en.wikipedia.org/w/index.php?title=Clemmensen_reduction&oldid=960785662, Creative Commons Attribution-ShareAlike License, This page was last edited on 4 June 2020, at 22:12. Clemmensen, E. Ber. Mitteilung. References. Legal. * The Clemmensen reduction is complementary to Wolff-Kishner CLEMMENSEN REDUCTION :- useful for CSIR NET JRF, GATE, SET, IIT JEE, IIT JAM, NEET, UPSC, GEO-Chemistry, UPSC Optional. [1][2][3] This reaction is named after Erik Christian Clemmensen, a Danish chemist. * There is a net flow of electrons from zinc to the carbonyl compound. easily gives ethyl benzene. * The C=O group is converted to CH2 group. Both these processes do these conversions via reducing the functional groups. * As there is no formation of alcohol during the reaction, this method is not useful to reduce alcohols to alkanes. Clemmensen reduction is complementary to Wolff-Kishner reduction, which also converts aldehydes and ketones to hydrocarbons, in that the former is carried out in strongly acidic conditions and the latter in strongly basic conditions. Clemmensen Reduction: Introduction Reaction principle Aldehydes and ketones are reduced to the corresponding methylene groups by treatment with concentrated hydrochloric acid …

The substrate must be tolerant of the strongly acidic conditions of the Clemmensen reduction (37% HCl). This is an example of  : (KERALA SET 2010). (Why? this side reaction can be avoided by employing Wolff-Kishner Therefore, these processes …

Acid-sensitive substrates that are stable to strong base can be reduced using the Wolff-Kishner reduction; a further, milder method for substrates stable to hydrogenolysis in the presence of Raney nickel is the two-step Mozingo reduction. For more information contact us at info@libretexts.org or check out our status page at https://status.libretexts.org. The Clemmensen reduction of 2-acetylfluorene may proceed through the corresponding carbinol, 2-(α-hydroxyethyl)fluorene, to the normal reduction product, 2-ethylfluorene. The probable mechanism is shown below. reduction, which The LibreTexts libraries are Powered by MindTouch® and are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. (III. [10], "Reduktion von Ketonen und Aldehyden zu den entsprechenden Kohlenwasserstoffen unter Anwendung von amalgamiertem Zink und Salzsäure", "Über eine allgemeine Methode zur Reduktion der Carbonylgruppe in Aldehyden und Ketonen zur Methylengruppe", "Über eine allgemeine Methode zur Reduktion der Carbonylgruppe in Aldehyden und Ketonen zur Methylengruppe.

We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739.

Missed the LibreFest? View Show abstract i am making series of … The two-step sequence of Friedel-Crafts acylation followed by Clemmensen reduction constitutes a classical strategy for the primary alkylation of arenes. INTRODUCTION This reaction was first reported by Clemmensen of Park Davis in 1913.

Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ … 3) In the following reaction, along with the reduction of carbonyl group, the -OH group is substituted by the -Cl group (side reaction). ), 1) Acetophenone when reacted with Zn (Hg) and HCl in ethyl alcohol * The Clemmensen reduction is used to conveniently reduce the carbonyl compounds, which are stable to strongly acidic conditions, to alkanes. * The Clemmensen reduction is used to conveniently reduce the carbonyl compounds, which are stable to strongly acidic conditions, Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. [4], The original Clemmensen reduction conditions are particularly effective at reducing aryl-alkyl ketones,[5][6] such as those formed in a Friedel-Crafts acylation. The mechanism for the Clemmensen reduction is not yet fully understood and there are two principal proposals: the ‘Carbanionic Mechanism’ and the ‘Carbenoid Mechanism’.

The key difference between Clemmensen and Wolff Kishner reduction is that the Clemmensen reduction involves the conversion of ketone or aldehydes into alkanes whereas the Wolff Kishner reduction involves the conversion of carbonyl groups into methylene groups.. [8][9] Mechanistic proposals generally invoke organozinc intermediates, sometimes including zinc carbenoids, either as discrete species or as organic fragments bound to the zinc metal surface. Watch the recordings here on Youtube! method. may be used to reduce acid sensitive compounds. * The C=O group is converted to CH 2 group. Clemmensen reduction is a chemical reaction described as a reduction of ketones (or aldehydes) to alkanes using zinc amalgam and concentrated hydrochloric acid. Ans: Nucleophilic substitution is not easy on sp2 carbon of benzene ring! Due to the heterogeneous nature of the reaction, mechanistic studies are difficult, and only a handful of studies have been disclosed. Scalable alternatives are molecular hydrogen with a catalyst under acidic conditions or, the trifluoroacetic acid-silane combination, such as triethylsilane or tetramethyldisiloxane. This alternative reduction involves heating a carbonyl compound with finely divided, amalgamated zinc in a hydroxylic solvent (often an aqueous mixture) containing a mineral acid such as HCl.

Several alternatives are available. The reaction of aldehydes and ketones with zinc amalgam (Zn/Hg alloy) in concentrated hydrochloric acid, which reduces the aldehyde or ketone to a hydrocarbon, is called Clemmensen reduction. A new experimental protocol has been established for the Clemmensen reduction of diosgenin and kryptogenin with the aim to prepare deuterated isotopomers of (25R)-26-hydroxycholesterol.

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