Propan-2-Ol Formula – Structure, Properties, Uses, Sample Questions

Propan-2-Ol belongs to the family of alcohols, it can be said easily because of the Ol in the name. It is basically secondary alcohol, in which the OH group is attached to the carbon atom only with one hydrogen present. Let’s take a look at the structure, properties, and uses of this secondary alcohol.

Structure of Propan-2-Ol 

The IUPAC name of isopropyl alcohol. It is the simplest secondary alcohol, as an isopropyl group linked with a hydroxyl group.

 

Chemical formula: CH₃-CHOH-CH₃

 

Preparation of Propan-2-Ol

• Biological process

Very less amount of propan-2-ol is produced by the diabetic ketoacidosis process.

• Hydration

This process can use low-quality propene. These processes give primarily propan-2-ol i.e. secondary alcohol rather than 1-propanol i.e. primary alcohol because adding water or sulfuric acid to propene follows Markovnikov’s rule. 

CH₃CHCH₂ + H₂O + H₂SO₄ ⇢ (CH₃)₂CHOH

Physical properties of propan-2-ol

1. It is a colorless, flammable compound. It has also an alcoholic strong smell. Unlike ethanol or methanol, propan-2-ol  is not miscible with salt solutions and can be separated from aqueous solutions by adding a salt such as sodium chloride.
2. Molar mass: 60.096 g/mol.
3. Density: 0.786 g/cc
4. Boiling point: 82.6 °C (180.7 °F; 355.8 K)
5. Solubility: It is miscible in water.

Chemical Properties and reactions

• Oxidation

Propan-2-Ol  is oxidized by chromic acid (H₂CrO₄) and formed acetone. It is a dehydrogenation process.

(CH₃)₂CHOH ⇢ (CH₃)₂CO + H₂  ⇡

• Dehydration

Propan-2-ol is dehydrated by using concentrated H₂SO₄ at 443K or using concentrated H₃PO₄ at 440K and produce propene and water.

(CH₃)₂CHOH ⇢  CH₂=CH-CH₃ + H₂O

• Halogenation

It is formed 2-bromopropane by using phosphorus tribromide.

(CH₃)₂CHOH ⇢ (CH₃)₂CHBr 

• Others

Propan-2-Ol is often used as both solvent and hydride source in the Meerwein-Ponndorf-Verley reduction and other transfer hydrogenation reactions.

Uses of propan-2-ol

• Medical uses: Basically it is used for rubbing alcohol, hand sanitizer, and disinfecting agent. 
• Solvent: It is the best used as a solvent. it evaporates quickly and leaves little to no trace compared to ethanol, and is relatively non-toxic.
• Laboratory use: It is relatively nontoxic than other preservatives like formaldehyde. Thus it is much more used than others.
• Cleaning: It is used as a cleaning fluid for oils, eyeglass, DVD, etc.

Sample Questions

Question 1: What is the structural difference between propanol and propan-2-ol?

Answer: 

The main and basic difference is propanol is a primary alcohol i.e. -OH group is linked with the 1st carbon molecule and propan-2-ol is secondary alcohol i.e. -OH group linked with the 2nd carbon molecule. Propanol is also structurally different because of its primary alcohol thus it makes it less stable than the propan-2-ol.

Question 2: Can propan-2-ol form azeotrope?

Answer: 

Propan-2-ol forms an azeotrope with water, which gives a boiling point of 80.37 °C (176.67 °F) and a composition of 87.7% by mass (91% by volume) propan-2-ol.

Question 3: What is the main mechanism of the oxidation reaction of propan-2-ol?

Answer: 

In the oxidation reaction, propan-2-ol reacts with oxidizing agent and forms propan-2-one. Here basically secondary alcohol like propan-2-ol is oxidized into ketone.  In the sodium, potassium dichromate solution with sulfuric acid or chromic acid gives propan-2-one with a chromium compound. And the hydrogen molecule of secondary carbon and hydroxyl group form water with the [O] of an oxidizing agent. After the removal of two hydrogen molecules, it generates ketone.

Question 4: What is Markovnikov’s rule?

Answer: 

Markovnikov’s rule is when a protic acid (HX) is added to an asymmetric alkene, alkyne, the acidic hydrogen attaches itself to the carbon having a greater number of hydrogen substituents whereas the halide group attaches itself to the carbon atom which has a greater number of alkyl substituents.

Question 5: How is Markovnikov’s rule implemented in the production of propan-2-ol?

Answer: 

Simply Markovnikov’s rule is hydrogen is added to the carbon with the most hydrogens and halide is added to the carbon with the least hydrogens. To form propan-2-ol from propane Markovnikov’s rule is implemented. When the alkene bond breaks and -OH join with carbon has the least hydrogen i.e. formation of propan-2-ol.

Question 6: Why propan-2-ol is commonly used as a solvent?

Answer: 

Propan-2-ol dissolves a wide range of non-polar compounds. It evaporates quickly and the types of available grades tend to not leave behind oil traces when used as a cleaning fluid, unlike some other common solvents. It is also relatively non-toxic. Thus, it is used widely as a solvent.

Question 7: Write down a simple example of a positional isomer of a three-carbon molecule with an alcohol group.

Answer: 

Propan-1-ol and propan-2-ol are the positional isomers that have the same molecular formula but differ from the position of the -OH group.