What is Isopropyl Alcohol?
Isopropyl alcohol, also well-known as 2-propanol, is one of the most predominant members of the organic compound family. Isopropyl alcohol was the first commercial synthetic alcohol; it was first produced in 1920 by chemists at New Jersey's Standard Oil Company (later Exxon Mobil), while studying petroleum by-products. It is easily synthesized by the propylene reaction with sulphuric acid, followed by hydrolysis.
IUPAC Name: Propan-2-ol
Molecular Weight: 60.1 g/mol
Synonyms
Isopropanol
2-propanol
Isopropyl alcohol
Propan-2-ol
Isopropyl Alcohol Chemical Formula:
Isopropyl alcohol formula can be written as C3H8O or CH3CHOHCH3 or (CH3)2CHOH
Isopropyl Alcohol Structure
It is a 1-propanol, and ethyl methyl ether structural isomer.
Isopropyl alcohol structural formula
(Image to be added soon) (Image to be added soon)
Properties
Physical properties of isopropyl alcohol
Isopropyl alcohol is miscible in water, chloroform, ethanol and ether
It dissolves ethyl cellulose, many oils, natural resins, polyvinyl butyral, gums and alkaloids.
Salting out
An azeotropeis formed when Isopropyl alcohol acts with water, which gives a boiling point of 80.37 ° C (176.67 ° F) and an isopropyl alcohol composition of 87.7 wt per cent (91 vol per cent).
Water-isopropyl alcohol mixtures have lower melting points.
It is slightly bitter in taste.
With decreasing temperature and freezing at −89°C (−128°F), isopropyl alcohol becomes ever more viscous.
Isopropyl alcohol is maximally absorbed in an ultraviolet - visible spectrum at 205 nm.
Chemical Properties of Isopropyl Alcohol
Isopropyl alcohol can be oxidized to acetone (equivalent ketone). This can be achieved with oxidizing agents such as chromic acid, or with isopropyl alcohol dehydrogenation over a heated copper catalyst.
(CH3)2CHOH → (CH3)2CO + H2
In reduction of Meerwein-Ponndorf-Verley and other transfer hydrogenation reactions, isopropyl alcohol is often used as both solvent and hydride source. Isopropyl alcohol can be converted to 2-bromopropane using tribromide phosphorus, or dehydrated to propene by sulfuric acid heating.
Like most alcohols, isopropyl alcohol reacts to the formation of alkoxides that can be called isopropoxides with active metals such as potassium. The aluminum reaction (initiated by a mercury tracer ) is used to prepare the aluminum isopropoxide catalyst
Isopropyl Alcohol Synthesis
This is produced primarily by combining water and propene in a hydration reaction or by hydrogenating acetone.
There are two ways for the hydration process, and both processes require distillation of the isopropyl alcohol from water and other by-products.
Isopropyl alcohol and water form an azeotrope, and simple distillation gives an alcohol content of 87.9% by weight isopropyl alcohol and 12.1% by weight water. Pure isopropyl alcohol (anhydrous) is formed by azeotropic distillation of the wet isopropyl alcohol using either diisopropyl ether or cyclohexane as azeotropic agents.
Indirect Hydration
In this process propene is reacted to form a mixture of sulfate esters with sulfuric acid. This method can use propene that is of low quality.
These processes primarily give isopropyl alcohol rather than1-propanol, because it follows Markovnikov 's rule to add water or sulfuric acid to propene. The subsequent hydrolysis by steam of these esters results in isopropyl alcohol, by distillation.
Diisopropyl ether is a major by-product of this process; it is reprocessed back to the process and hydrolyzed to give the preferred product.
(Image to be added soon)
Direct Hydration
In the presence of solid or supported acid catalysts, direct hydration reacts to propene and water, either in gas or liquid phase, at high pressures.This type of process usually requires propylene with higher purity (> 90 per cent)
Isopropyl Alcohol Uses
As Solvent
A number of non-polar compounds is reduced by isopropyl alcohol. This also evaporates rapidly, leaving almost zero traces of oil compared with ethanol, and is relatively non-toxic compared with alternative solvents. It is thus widely used as a solvent and as a purifying fluid
Intermediate
Alcohol is esterified to give another solvent, the isopropyl acetate. It reacts with carbon disulfide and sodium hydroxide to provide a reagent for sodium isopropylxanthate, herbicide.
For Medical purpose:
Rubbing alcohol, hand sanitizer, and disinfectant pads typically contain a water solution of 60–70 per cent isopropyl alcohol or ethanol. Water is needed to open bacterial membrane pores which act as a gateway for isopropyl alcohol.
As an Anesthetic
While isopropyl alcohol can be used for anesthesia, this use is prohibited because of its many negative attributes or drawbacks. Isopropyl alcohol can also be used as a solvent, similar to ether
Automotive
Isopropyl alcohol is an important ingredient in fuel additives for the "gas dryer."
Laboratory
Isopropyl alcohol is a biological preservative which provides a comparatively non - toxic alternative to formaldehyde and other synthetic preservatives. 70–99 per cent of isopropyl alcohol solutions are used to preserve specimens.
FAQs on Isopropyl Alcohol
1. What is isopropyl alcohol, and what are its IUPAC name and chemical formula?
Isopropyl alcohol, an organic compound, is a secondary alcohol. Its official IUPAC name is propan-2-ol. The chemical formula for isopropyl alcohol is C₃H₈O, and its condensed structural formula is written as CH₃CH(OH)CH₃, which shows the hydroxyl (-OH) group attached to the central carbon atom of a three-carbon chain.
2. What are the primary uses of isopropyl alcohol in household and industrial settings?
Isopropyl alcohol is a versatile compound with several important applications based on its properties as a solvent and disinfectant. Key uses include:
- Antiseptic: It is the main ingredient in rubbing alcohol (typically 70% solution) used for sterilising skin before injections and for disinfecting minor cuts.
- Solvent: It effectively dissolves oils, gums, alkaloids, and resins, making it a common component in cosmetics, lotions, and shellacs.
- Cleaning Agent: Due to its rapid evaporation and ability to dissolve oils without leaving a residue, it is ideal for cleaning electronic components like computer chips and contact pins.
- Fuel Additive: It is used as a 'gas dryer' in fuel additives to solubilise water, preventing it from freezing in fuel lines during cold weather.
3. How does the structure of isopropyl alcohol as a secondary alcohol affect its oxidation reaction?
The structure of isopropyl alcohol as a secondary alcohol (where the hydroxyl-bearing carbon is attached to two other carbons) directly determines its oxidation product. When oxidised using agents like chromic acid (H₂CrO₄), it is converted into a ketone, specifically acetone ((CH₃)₂CO). This is different from primary alcohols, which oxidise to aldehydes and then carboxylic acids, and tertiary alcohols, which are resistant to oxidation.
4. Why is a 70% solution of isopropyl alcohol generally a more effective disinfectant than a 99% solution?
A 70% solution of isopropyl alcohol is a more potent disinfectant because the presence of 30% water is critical for its action. Water acts as a catalyst and slows down the evaporation process, increasing surface contact time. More importantly, it helps in denaturing the proteins of a microbe's cell wall, allowing the alcohol to penetrate the cell and act on its internal components. In contrast, a 99% solution coagulates the external surface proteins too quickly, which forms a protective layer and prevents the alcohol from effectively entering and killing the microbe.
5. How is isopropyl alcohol commercially manufactured from propene?
The main industrial method for producing isopropyl alcohol is the hydration of propene. This process follows Markovnikov's rule, which states that the hydrogen atom adds to the carbon with more hydrogen atoms, and the hydroxyl group adds to the carbon with fewer hydrogen atoms. This ensures the product is propan-2-ol (isopropyl alcohol) rather than propan-1-ol. The two main pathways are:
- Indirect Hydration: Propene is first reacted with sulfuric acid to form sulfate esters, which are then hydrolysed with steam to yield isopropyl alcohol.
- Direct Hydration: Propene gas and water (as steam) are passed over a solid acidic catalyst at high pressure and temperature to produce isopropyl alcohol directly.
6. What are the key differences between isopropyl alcohol and ethanol?
While both are common alcohols, they have distinct differences in structure and application:
- Structure: Ethanol (CH₃CH₂OH) is a primary alcohol. Isopropyl alcohol (CH₃CH(OH)CH₃) is a secondary alcohol.
- Toxicity: Isopropyl alcohol is significantly more toxic than ethanol upon ingestion and is unsafe for human consumption.
- Solvent Properties: Isopropyl alcohol is generally more effective at dissolving lipids and oils, making it a preferred choice for cleaning electronics and as a degreaser.
- Odor: Isopropyl alcohol has a sharper, more medicinal odour compared to the milder scent of ethanol.
7. What is an azeotrope and how does this property impact the purification of isopropyl alcohol?
An azeotrope is a mixture of liquids that has a constant boiling point and composition throughout distillation. Isopropyl alcohol and water form an azeotrope at a concentration of about 87.7% isopropyl alcohol by weight. This means that simple distillation of an aqueous solution of isopropyl alcohol cannot yield a purity greater than 87.7%. To obtain pure (anhydrous) isopropyl alcohol, a process called azeotropic distillation is required, where another substance (an entrainer) is added to break the azeotrope and allow for the separation of water.
