Stepwise Explanation of the Corey House Reaction for Students
Corey's synthesis, the Wurtz reaction, the reduction of alcohols and aldehydes, Kolbe's electrolysis, the hydrogenation of alkenes, and the Grignard reaction are a few techniques for creating alkanes. Among the techniques available, the traditional Corey house reaction involves significant benefits in that it can produce symmetric, unsymmetrical, straight-chain, and branched-chain alkanes.
Additionally, utilizing primary alkyl halide with a variety of lithium dialkyl copper, spanning from primary to tertiary, enables the production of large yields of alkanes. The idea and workings of Corey house reactions can be utilized for so many different things. Additional studies were conducted to further enhance this synthetic method, opening the door to the production of several organic molecules that might be used as medicines to treat a wide range of illnesses. So this article provides deep knowledge on the concept of Corey house reaction with certain examples and mechanisms.
What is Corey House Reaction?
In order to create larger alkanes, 2 alkyl groups can be joined by the coupling mechanism. This flexible strategy is known as the Corey-House reaction.
Nevertheless, this reaction seldom functions effectively in practice because of metal-halogen exchanges and the creation of significant quantities of by-products from elimination or reduction separate from the employment of metal acetylides as nucleophiles. The Corey-House reaction provides a generic and very efficient mechanism for connecting two alkyl groups or an alkyl group and an aryl group in order to address this issue.
Mechanism of Corey House Reaction
The mechanism of Corey house reaction is explained through the following example:
\[{R_2}CuLi + R'X \to RR' + RCu + LiX\]
There are two steps in this reaction above. In order to create an alkyl lithium compound, R-Li, the alkyl halide is reacted with lithium metal and solvated in dry ether.
Primary, secondary, or tertiary alkyl halides can be the beginning R-X:
\[RX + 2Li \to RLi + LiX\]
Alkyl-lithium and cuprous iodide (CuI) are combined in the second stage to create lithium dialkyl cuprate. Gilman Reagents are the name for the main product of this reaction. Identical to Grignard and organolithium reagents, Gilman reagents are a resource of nucleophiles with carbanion-like properties. By using the Corey-House reaction, the Gilman reagent interacts with organic halides to convert the halide group into an R group, enabling the production of complex compounds from basic constituents.
\[2RLi + CuI \to {R_2}CuLi + LiI\]
The second alkyl halide is then utilized to convert the lithium dialkyl cuprate that couples to the compound:
\[{R_2}CuLi + R'X \to RR' + RCu + LiX\]
Cross-products develop if the second alkyl halide differs from the initial. It is crucial to remember that the second alkyl halide needs to be a methyl halide, benzyl halide, primary alkyl halide, or secondary cyclo alkyl halide for the mechanism to be effective. This mechanism is important for synthesising organic molecules because of how straightforward it is.
Example of Corey House Reaction
The Corey house reaction example is provided below:
\[{\left( {C{H_3}} \right)_2}CuLi + C{H_3}C{H_2}Br \to C{H_3}C{H_2}C{H_3} + C{H_3}Cu + LiBr\]
In the environment of dry ether, lithium dimethyl cuprate combines with ethyl bromide to produce propane together with lithium bromide and methyl copper.
As a result of the reaction between methyl bromide (an alkyl halide) and lithium metal in the environment of dry ether, methyl lithium and lithium bromide are produced. In order to create lithium dimethyl cuprate, or Gilman reagent, methyl lithium is first reacted using cuprous iodide.
Advantages of Corey House Reaction over Wurtz Reaction
Any kind of alkane, whether straight chained or branching chain, with an even or odd number of carbon atoms, can indeed be synthesised utilizing the Corey-House reaction. The primary usage of this reaction is the production of higher alkanes. This reaction is thus more appropriate than the Wurtz reaction.
Whenever primary alkyl halide and primary, secondary, or tertiary lithium dialkyl copper are employed, Corey house reaction can generate massive outputs of alkanes.
The most effective and accessible method for synthesising complex organic compounds is the Corey-House reaction, which applies coupling pairs, functional group endurance, and simple procedure. Additionally, it works well at room temperature.
Interesting Facts
The four organic chemists that collaborated to create this important Corey house reaction were Herbert O. House of the Georgia Institute of Technology, Gary H. Posner of Johns Hopkins University, G.M. Whitesides of MIT, and E.J. Corey of Harvard University.
The alternative names for the Corey-House reaction include Corey-Posner, Whitesides-House reaction, and other permutations.
These lithium dialkyl cuprate or organ copper compounds are frequently referred to as Gilman reagents in recognition of Henry Gilman, who created them.
Keywords to Remember Features
Three steps make up the Corey-House reaction. Alkyl halide can be converted to alkyl lithium molecules by treating it with lithium metal, solvating it in dry ether, and then treating the alkyl lithium compound using cuprous halide to produce dialkyl lithium cuprate.
The reagents employed in this synthesis are cuprous iodine and lithium metal. The substrates can be two alkyl halides that are identical or distinct. This process employs the coupling reaction as its mechanism. Lithium dialkyl cuprate and alkyl halide effectively couple, and the result is the production of hydrocarbons.
Lithium dialkyl cuprate also couples with vinyl and phenyl halide.
FAQs on Corey House Reaction: Mechanism and Key Examples
1. What is the Corey-House reaction? Please provide a general example.
The Corey-House reaction, also known as the Corey-Posner, Whitesides-House synthesis, is a versatile method in organic chemistry used to synthesize alkanes, particularly unsymmetrical alkanes, with high yield. It involves the reaction of a lithium dialkylcuprate (Gilman reagent) with an alkyl halide. A general example is the reaction between lithium dimethylcuprate and ethyl iodide to form propane: (CH₃)₂CuLi + CH₃CH₂I → CH₃CH₂CH₃ + CH₃Cu + LiI.
2. What are the key steps involved in the mechanism of the Corey-House synthesis?
The Corey-House synthesis mechanism primarily consists of two main steps:
- Step 1: Formation of the Gilman Reagent: An alkyl halide (R-X) is first treated with lithium metal in dry ether to form an alkyllithium compound (R-Li). This alkyllithium is then reacted with cuprous iodide (CuI) to produce the lithium dialkylcuprate ((R)₂CuLi), also known as the Gilman reagent.
- Step 2: Coupling Reaction: The prepared Gilman reagent is then reacted with a second, different alkyl halide (R'-X). One of the alkyl groups from the Gilman reagent displaces the halide from the second alkyl halide, forming a new carbon-carbon bond and resulting in the desired alkane (R-R').
3. What is a Gilman reagent and how does it differ from a Grignard reagent?
A Gilman reagent is a lithium dialkylcuprate with the general formula R₂CuLi. It serves as a source of a 'soft' nucleophilic alkyl group. The key difference lies in its reactivity compared to a Grignard reagent (R-MgX). Gilman reagents are less basic and less reactive. This lower reactivity makes them more selective, allowing them to participate in coupling reactions with alkyl halides without attacking other sensitive functional groups like esters or ketones, which a Grignard reagent would readily attack.
4. Why is the Corey-House reaction preferably carried out with primary alkyl halides in the coupling step?
The coupling step of the Corey-House reaction proceeds via a mechanism similar to an Sₙ2 reaction. For this nucleophilic substitution to be successful, the carbon atom bearing the halogen must be accessible. Primary alkyl halides are ideal because they have minimal steric hindrance. Secondary halides can also be used, but tertiary halides are too sterically hindered. When a tertiary halide is used, the Gilman reagent acts as a base, leading to an elimination reaction (E2) as the major pathway, which produces an alkene instead of the desired alkane.
5. What is the main advantage of the Corey-House synthesis over the Wurtz reaction for preparing alkanes?
The primary advantage of the Corey-House synthesis is its ability to effectively prepare unsymmetrical alkanes (R-R') with a good yield. In contrast, the Wurtz reaction is only efficient for preparing symmetrical alkanes (R-R). If two different alkyl halides are used in a Wurtz reaction, it results in a mixture of three different alkanes (R-R, R'-R', and R-R'), which are often difficult and impractical to separate.
6. In which chapter of the CBSE Class 11 and 12 Chemistry syllabus is the Corey-House reaction covered?
The Corey-House reaction is an important topic for preparing alkanes and is explicitly covered in the NCERT Class 11 Chemistry syllabus, as per the 2025-26 curriculum. You can find it in Unit 8: Organic Chemistry – Some Basic Principles and Techniques, under the section for preparation of hydrocarbons. Its principles are also highly relevant for understanding reactions in Class 12, Unit 6: Haloalkanes and Haloarenes.
7. How can you synthesize 2-methylpropane using the Corey-House reaction?
To synthesize 2-methylpropane ((CH₃)₂CH-CH₃), you would react lithium diisopropylcuprate with methyl iodide. The steps are as follows:
- Step 1: Prepare the Gilman reagent, lithium diisopropylcuprate. Start with 2-bromopropane, react it with lithium to get isopropyllithium, and then react that with CuI. `((CH₃)₂CH)₂CuLi`.
- Step 2: React the Gilman reagent with methyl iodide (CH₃I). `((CH₃)₂CH)₂CuLi + CH₃I → (CH₃)₂CH-CH₃ + (CH₃)₂CH-Cu + LiI`. This forms the target molecule, 2-methylpropane.
8. What is the specific role of copper in the Gilman reagent during the Corey-House reaction?
The copper atom in the Gilman reagent (R₂CuLi) plays a crucial role in moderating the reactivity of the carbanion-like alkyl group. Unlike the highly reactive 'hard' nucleophiles in organolithium or Grignard reagents, the copper-carbon bond creates a 'soft' nucleophile. This 'soft' nature makes the alkyl group highly effective at attacking the carbon of an alkyl halide (an Sₙ2 reaction) while being unreactive towards 'hard' electrophiles like the carbonyl carbon of ketones or esters. This chemoselectivity is the key to the synthetic power of the Corey-House reaction.
