Multistep Synthesis.

Organic chemistry is a branch of chemistry that deals with the reaction of organic molecules. During the study of organic chemistry, one is introduced to different functional groups. These functional groups include alcohol, alkene, carboxylic acids, alkane, esters, ethers, alkyl halides, ketones, aldehyde, and so on.

To know how the reaction proceeds, it is important to know how to identify the functional groups of different molecules. Knowing these functional groups will help you know what reagent is required to convert one molecule to another.

Conditions for multistep synthesis reactions.

Correct reagent.

A reagent is a chemical substance used to convert one molecule to another. The reagent must be correct and in the right concentration to get the correct product.

There must be a good nucleophile. 

A nucleophile is also called a Lewis base. It is a substance that has lone pairs which can be donated. It readily gives electrons to form a new covalent bond. Examples of nucleophiles are H₂O, NH₃, Cl-, Br-, I- etc.

Presence of an electrophile

An electrophile is also called a Lewis acid. It is a substance that has empty orbitals and can accept electrons from a nucleophile. For an atom to be a good nucleophile, it must be bonded to an electronegative atom in that a bond is broken when a nucleophile approaches. An example of an electrophile is a carbon bonded to an alkyl halide or a carbonyl carbon.

A leaving group.

A leaving group is a substance that cleaves when a nucleophile forms a new bond with the electrophile. It might be present or not, depending on the compound. For instance, a leaving group is unnecessary if it’s a carbonyl carbon.

The reactions of alkene and alkyl halide are the most common substance that confuses many students. This is due to the number of reactions they can undergo to form different products.

Multistep synthesis of alkyl halides Reactions.. 

Before writing the reaction synthesis, we must first understand what alkyl halide looks because different alkyl halides undergo different reactions.

The four classes of alkyl halides are;

• Methyl alkyl halide
• Primary alkyl halides are also denoted as 1⁰ alkyl halides.
• Secondary alkyl halides are also denoted as 2⁰ alkyl halides.
• Tertiary alkyl halides are also denoted as 3⁰ alkyl halides.

Reactions of alkyl halide. 

Alkyl halides undergo substitution or elimination reactions because of the good leaving groups. The conditions and reagent will determine if the reaction will be an elimination or substitution reaction.

A substitution reaction is a reaction in which another substance replaces an alkyl halide. Under these reactions, compounds undergo either SN1 or SN2 reactions depending on the reagents given.

Example of SN1 reaction of alcohol to an alkyl halide.

Example of SN2 reaction of alcohol to an alkyl halide.

An elimination reaction is a reaction in which an alkyl halide is converted to an alkene. Under an elimination reaction, compounds undergo either E1 or E2, depending on the reagent.

Examples of E1 reaction of the alkyl halide to an alkene

 Alkyl halides are good leaving groups because they are very stable after cleaving.

Examples of E2 reactions of alkyl halides to form alkene;

Multistep synthesis examples.

In these reactions, several steps convert one compound to the desired compound. It could be two steps or more. The following reactions are examples of multistep synthesis.

1) Multistep synthesis for the conversion of alkene to a ketone.

An example is when alkene is converted to a ketone. To achieve this, an alkene is first converted to alcohol by a suitable. Then using a suitable oxidizing agent, the alcohol is then converted to a ketone.

2) Multistep synthesis of benzilic acid from benzaldehyde.

The reaction mechanism for converting benzaldehyde to benzylic acid is shown below.

Steps: 

• The reaction of two benzaldehyde molecules with thiamine hydrochloride to form benzoin.
• Benzoin is converted to benzyl using nitric acid (HNO₃)
• Lastly, benzyl is converted to benzylic acid using potassium hydroxide in alcohol in acid. (KOH in Alcohol, then H₃O+).

Reactions steps are;

3) Multistep reaction for the conversion of benzene to benzaldehyde. 

This reaction can be achieved via several routes. Some of the routes are

1st route:

• Benzene is reacted with Br₂/FeBr₃ to form bromobenzene
• Bromobenzene is reacted with Mg in ether to form a Grignard reagent which will later act as the nucleophile.
• The reaction of the Grignard reagent with formyl chloride.

2nd route;

• Benzene is reacted with CO followed by HCl, anhydrous AlCl3.

3rd route:

• Benzene is reacted with CHCl₃, followed by NaOH.

4) Multistep synthesis of benzene to m-bromo aniline.

Steps

• Benzene is converted to nitrobenzene using HNO₃ & H₂SO₄.
• Nitrobenzene is converted to 3-bormo nitrobenzene using Br₂ and FeBr₃
• 3-bormo nitrobenzene is converted to m-bromo aniline using Fe in HCl.

These are just examples of multiple syntheses among many. If you need help with organic chemistry homework, click on the link below, and we will be glad to help.

Importance of organic multistep synthesis. 

Synthesis reactions help chemists and researchers to synthesize compounds that do not occur naturally in the lab. Pharmaceutical companies use organic multistep synthesis to produce drugs such as aspirin and penicillin. Other drugs formed by multistep synthesis are tamoxifen, quinine, rufinamide, etc. this is why organic chemistry is important in biology.

Multistep synthesis homework help

The organic chemistry course is very broad, and most students find it difficult to understand these complex syntheses. If you have organic chemistry homework that you need help with, we have organic chemistry expert tutors who are willing to help you with your chemistry assignment.

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