Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Physics
Chemistry
Biology
Mathematics
English
Economics
Psychology
Social Studies
Fashion Studies
Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
Preparation of Alcohols
Introduction
Alcohols are vastly used in daily life. It is not only used as an intoxicating beverage, it is also used in different industries. Alcohols are obtained by replacing a hydrogen atom by the hydroxyl functional group(-OH) and attached with saturated hydrocarbons. For example, in methanol $\mathrm{(CH_{3}OH)}$ there is one saturated carbon atom, one hydroxyl group (-OH) and three hydrogen atoms. The types of alcohols are: primary alcohol, secondary alcohol and tertiary alcohol.
What are Alcohols?
Alcohols are defined as an organic compound which contains at least one hydroxyl group (- OH) and bonded with a carbon chain. Generally, alcohol is used to denote the primary alcohol, that is ethanol $\mathrm{(C_{2}H_{5}OH)}$ and methanol $\mathrm{(CH_{3}OH)}$. Ethanol is the main component of alcoholic drinks and also present in drugs.
According to the IUPAC chemical naming, if hydroxyl group is present as one of the main functional group then in the suffix of the name (-ol) will appear. If another functional group is present in the compound the hydroxyl group is referred to as hydroxy.
Methods of Preparation of Alcohols
Alcohols are prepared using various methods. The different methods of alcohol formation are given below −
Grignard Synthesis Method − In the Grignard synthesis method Grignard reagent is used. With the help of Grignard reagents all three types of alcohol i.e., primary, secondary and tertiary can be formed. Alcohols are formed when Grignard reagent and carbonyl compound are interacted with each other and the hydrolysis is done. The reaction with Formaldehyde produces primary alcohol, the reaction with other aldehydes leads to secondary alcohol and that with ketones yields tertiary alcohol.
Figure 1 − Methods involved in Alcohol preparation
Acid Catalysed Hydration of Alkenes Method − In this method, when alkenes interact with water in the presence of a catalyst it forms alcohol. The indirect way of hydration is accomplished by adding the Sulphuric acid to the alkene followed by hydrolysis.
Hydroboration of Alkenes Method − When alkenes are interacted with Diborane it gives Trialkyl Boranes. When Trialkyl Boranes are oxidised with Alkaline Hydrogen Peroxide it forms alcohol.
Hydrolysis Of Halides Method − When Alkyl halides and aqueous solution of an Alkali Hydroxi
Hydroformylation of Alkenes Method − In industry this method is commonly used for alcohol formation. In this method Olefins, whose molecular weight is lower, react with Hydrogen and Carbon Monoxide (CO), in the presence of catalyst. Then alcohol is formed from that aldehyde by hydrogenation.
Reduction of Aldehydes and Ketones − In this method, aldehydes and ketones are reduced from the corresponding alcohol by catalytic hydrogenation process, in the presence of Hydrogen and some catalyst. Some commonly used catalysts are nickel, Platinum. Lithium Aluminium Hydride $\mathrm{(LiAlH_{4})}$ is used as a reducing agent for treating ketones and aldehydes.
Oxymercuration and Demercuration of Alkanes − In this method, Oxymercuration and Demercuration of Alkenes and Mercuric Acetate react with water and Tetrahydrofuran and form Mercury which is alkyl. Then Sodium Borohydride $\mathrm{(NaBH_{4})}$ is treated with this. This method is also commonly used in alcohol preparation.
Reaction of Nitrous Acid and Primary Amines − In this preparation of alcohol a reaction happens between Nitrous acid and primary amines. As an outcome of this reaction other than alcohol preparation a colourless and odourless gas is produced along with nitrogen. For the reaction, it doesn’t have a single equation. For example, $\mathrm{CH_{3}NH_{2}}$ gives $\mathrm{CH_{3}\:-\:O\:-\:N\:=\:O\:or\:CH_{3}OCH_{3}}$.
Reduction of Acids − Among the alcohol reducer, Lithium Aluminium Hydride is used to reduce the acid to an alcohol.
$$\mathrm{R\:-\:X\:+\:KOH\:(aq)\:\rightarrow\:R\:-\:OH\:+\:KH}$$
$$\mathrm{CH_{3}NH_{2}\:+\:2HNO_{2}\:\rightarrow\:CH_{3}\:-\:O\:-\:N\:=\:O\:+\:2H_{2}O\:+\:N_{2}}$$
$$\mathrm{2CH_{3}NH_{2}\:+\:2HNO_{2}\:\rightarrow\:CH_{3}OCH_{3}\:+\:2N_{2}\:+\:3H_{2}O}$$
$$\mathrm{4RCOOH\:+\:3LiAlH_{4}\:\rightarrow\:4RCH_{2}OH}$$
Discussion on Fermentation
In this method the complex organic compounds decomposes into simpler organic compounds by the enzyme activity and it is a slower process. Enzymes are Nitrogenous proteins, non-living macromolecules. Enzymes are normally got from living organisms. In this processes $\mathrm{CO_{2}\:and\:CH_{4}}$ gasses are evaluated. A lot of energy releases during this process and it is also exothermic in nature. In alcoholic fermentation, sugar converts into ethyl alcohol by yeast.
Conclusion
Alcohol is a widely used organic compound. There are two terms in every common name of alcohol, the first part is derived from the alkyl group of the compound and the second part is the term alcohol. For example, $\mathrm{CH_{3}OH}$ is Methyl alcohol. Different types alcohols are prepared by different methods but there are some methods by which all three types (primary, secondary and tertiary) of alcohols can be prepared by replacing the Hydrogen atom by Hydroxyl functional group(-OH) and attached with the Carbon chain.
FAQs
1. What is the difference between aldehydes and ketones?
Aldehydes and ketones both are organic compounds and both of them contain Carbonyl group (-CO). In aldehyde Carbonyl functional group attached with a Carbon atom at the last of the Carbon chain. In ketone carbonyl functional group attached with a carbon atom in between the Carbon chain.
2. What is the difference between phenols and alcohols?
Alcohols are organic compounds which contain one Hydroxyl functional group (-OH) that is attached to a saturated Carbon atom. Where phenols are also an organic compound and also contain Hydroxyl functional group (-OH) which attached to an aromatic hydrocarbon.
3. Write three properties of Ethanol?
The three properties of ethanol involves that it is colourless liquid with a pleasant odour and a burning taste and it is flammable in nature. In addition, it normally it is used to dissolve other chemical substances.
4. What is an organic compound?
Organic compounds are chemical compounds which contain one or more carbon atoms and this carbon atoms are covalently linked with other atoms like Hydrogen, Nitrogen and Oxygen.
