Name: grignard reagents in alcohol synthesis
Uploaded: 2023-04-30T18:28:39.000Z
Duration: 2 min
Channel: JoVE

Alcohols are prepared from carbonyl compounds via carbonyl addition reactions using strong bases like Grignard reagents.
Grignard reagents are organomagnesium halides with a characteristic C&#8211;Mg covalent bond.
The greater electronegativity of carbon induces an ionic character in the bond, resulting in a partial negative charge on the carbon atom. This makes the Grignard reagent a strong carbon nucleophile.
On the other hand, carbonyl compounds such as aldehydes and ketones function as carbon electrophiles.
In a Grignard reaction, as magnesium coordinates to the carbonyl oxygen, oxygen pulls the electron density from the carbonyl group, making the carbonyl carbon a better electron acceptor and a stronger electrophile.
The carbanionic group of the Grignard reagent adds to the electrophilic carbon, forming a &#963; bond in the alkoxide ion.
In the subsequent step, the alkoxide is protonated using either dilute acid or water to form the corresponding alcohol.
Different classes of alcohols are formed depending on the carbonyl functional group undergoing the reaction.
Barring formaldehyde, which gives primary alcohols, all other aldehydes give secondary alcohols on reaction with a Grignard rea

alcohols from carbonyl compounds: grignard reaction

Alcohols from Carbonyl Compounds: Grignard Reaction

Grignard reagents are one of the most commonly used reagents used to synthesize alcohols from carbonyl compounds. Grignard reagents are organomagnesium halides with a highly polar carbon&#8211;magnesium bond. Due to the partial ionic nature of&#160;the C&#8211;Mg bond, the carbon functions as a strong nucleophile and attacks electrophiles like carbonyl carbon.
Magnesium from the reagent coordinates with carbonyl oxygen, further reducing the carbonyl carbon&#39;s electron density. Thus, the carbonyl carbon is a stronger electrophile. The carbanionic group of the reagent then attacks this electrophilic carbon to form an alkoxide ion. In the following step, the alkoxide ion is protonated using dilute acid or water to give alcohol.
Different classes of alcohols are formed depending on the type of carbonyl compounds undergoing the reaction. When reacted with a Grignard reagent, formaldehyde converts to a primary alcohol, while all other aldehydes form secondary alcohols. Ketones, on the other hand, give tertiary alcohols. The carbonyl group in a carboxylic acid does not welcome nucleophilic additions with the Grignard reagent. Instead, the reagent acts as a strong base and abstracts a proton from the acid&#39;s &#8211;COOH group. The derivatives of carboxylic acid, such as esters and acid chlorides, react with two equivalents of Grignard reagent to form tertiary alcohols with a ketone intermediate.

Grignard reagents are one of the most commonly used reagents used to synthesize alcohols from carbonyl compounds. Grignard reagents are organomagnesium ...

alcohols-from-carbonyl-compounds-grignard-reaction

Education

JoVE Core

Organic Chemistry

Unit 1

Alcohols and Phenols

KEY TERMS AND CONCEPTS

grignard reagents in alcohol synthesis

Grignard reagents are key tools for making alcohols from carbonyl compounds. They are organomagnesium halides with a highly polar carbon–magnesium bond. Because this bond is partly ionic, the carbon acts as a strong nucleophile. It attacks the carbonyl carbon, which is the electrophilic part of a carbonyl group.

Magnesium in the reagent also helps the reaction move forward. It coordinates with the carbonyl oxygen and lowers the electron density on the carbonyl carbon. This makes the carbonyl carbon even more electrophilic. The carbon from the Grignard reagent then adds to it and forms an alkoxide ion. In the last step, dilute acid or water protonates the alkoxide to give an alcohol.

The type of alcohol formed depends on the carbonyl compound. Formaldehyde gives a primary alcohol when it reacts with a Grignard reagent. Other aldehydes form secondary alcohols. Ketones form tertiary alcohols.

Carboxylic acids do not undergo this nucleophilic addition in the usual way. Instead, the Grignard reagent acts as a strong base and removes the proton from the acid’s –COOH group. Carboxylic acid derivatives, such as esters and acid chlorides, react with two equivalents of Grignard reagent. They form tertiary alcohols through a ketone intermediate.

Grignard Reagents in Alcohol Synthesis

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Grignard reagents are key tools for making alcohols from carbonyl compounds. They are organomagnesium halides with a highly polar carbon–magnesium bond. Because this bond is partly ionic, the carbon acts as a strong nucleophile. It attacks the carbonyl carbon, which is the electrophilic part of a carbonyl group. Magnesium in the reagent also helps the reaction move forward. It coordinates with the carbonyl oxygen and lowers the electron density on the carbonyl carbon. This makes the carbonyl...

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key terms and concepts

Learn how Grignard reagents add to carbonyl compounds to form alcohols, including primary, secondary, and tertiary products from aldehydes, ketones, and esters.

Grignard Reagents in Alcohol Synthesis | JoVE K12

organic chemistry

JoVE Core Organic Chemistry explains basic concepts of stereochemistry, reactions, and mechanisms using concise and easy-to-understand animated video lessons. Additionally, the scientist-in-action videos demonstrate the application of related concepts in classical and original research experiments performed in today's laboratories worldwide.

Grignard Reagents in Alcohol Synthesis

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