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Isopropanol

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Introduction

Isopropyl alcohol, which is often known as isopropanol or 2-propanol, is a flammable and colourless chemical compound. CH3CHOHCH3 is the isopropanol formula and it has a strong odour. The simplest example of a secondary alcohol is an isopropyl group linked to a hydroxyl group, in which the alcohol carbon atom is attached to 2 other carbon atoms. It is a structural isomer of 1-propanol and ethyl methyl ether. The IUPAC name is given as propan-2-ol.

It's a common ingredient in antiseptics, disinfectants, and detergents, and it's used in the manufacture of a wide variety of industrial and household chemicals.


Isopropanol Structure

Isopropanol formula is CH3CHOHCH3. The isopropanol structure or the Isopropyl Alcohol Structure – C3H8O can be represented as follows:


Properties

Water, ethanol, and chloroform are all miscible with isopropyl alcohol. Ethyl cellulose, polyvinyl butyral, a range of oils, alkaloids, gums, and natural resins are all dissolved by it. Unlike ethanol or methanol, isopropyl alcohol is not miscible with salt solutions and can be separated from aqueous solutions by adding a salt such as sodium chloride. The separation of concentrated isopropyl alcohol into a separate layer is referred to as salting out.

When isopropyl alcohol reacts with water, it forms an azeotrope with a boiling point of 80.37 °C (176.67 °F) and a bulk content of 87.7% isopropyl alcohol (91%) . The melting points of alcohol mixes are low. It has a faint bitter flavour and should not be taken.

Isopropyl alcohol becomes increasingly viscous as the temperature drops, and it freezes at 89 ° C (128 ° F).

In the ultraviolet-visible spectrum, isopropyl alcohol has a maximum absorbance of 205 nm.


Function of Isopropanol in DNA Extraction

Let us study the function of isopropanol in dna extraction from the initial stage.


Initial Phase of DNA Extraction from Blood and Other Cell Tissue

The DNA extraction procedure starts with sonication, agitation, and the addition of SDS detergents to mechanically separate the nuclear contents from the remainder of the cell. During this stage of the procedure, researchers generally add ammonium, sodium acetate, or similar salts to further break down cell components and then extract off the DNA linked proteins.


Isopropanol Precipitation of DNA

Since DNA is insoluble in ethanol and isopropanol, adding alcohol to the solution and centrifuging it will induce the DNA proteins to separate from the solution. When the concentration of DNA in a sample is high, adding ethanol causes a white precipitate to form almost immediately. Isopropanol may work better than ethanol to precipitate available proteins if the DNA concentration in the sample is low. In addition, isopropanol is frequently used to precipitate DNA from huge volumes because the isopropanol uses less alcohol.

Ethanol and isopropanol can also be used to wash away any salt residue. The precipitated DNA protein will form a pellet after being washed in alcohol and centrifuged, which can then be washed in alcohol again, dried, and re-suspended in a Tris or TE buffer. Simply place the cleaned pellet on the lab table for a few minutes, as overdrying the sample can denature the DNA. If isopropanol was used instead of ethanol during the extraction, the sample may not stick as well to the tube and may require more drying time.


Toxicity

After oral administration, isopropanol is fast absorbed (within 30 minutes) and well absorbed (within 70% bioavailability). Alcohol dehydrogenase converts isopropanol to acetone in a first-order, concentration-dependent way. Isopropanol's apparent first-order metabolism is most likely the product of significant acetone clearance in the acetone.

Approximately 80% of systemic isopropanol is converted to acetone, with the other 20% eliminated unchanged through the kidneys. Isopropanol can be excreted in small amounts through the lungs. Isopropanol metabolism will be competitively antagonised by ethanol via alcohol dehydrogenase, resulting in a longer isopropanol t\[_{1/2}\].


Toxicosis

70% of rubbing alcohol, antifreeze, detergents, window cleaning products, and disinfectants include isopropanol (isopropyl alcohol), which has a molecular weight of 60 Da. Although toxicity by inhalation and topical absorption has been described, the most common cause of poisoning in humans is ingestion. Because of its bitter taste, isopropanol toxicosis is uncommon in domestic animals. It was described in a horse who was given isopropanol for colic by mistake by nasogastric intubation; the isopropanol was mistaken for mineral oil (Somerville and Plumlee, 1996).


Toxicokinetics

Isopropanol is approximately two times as toxic as ethanol. It is rapidly absorbed from the GI tract, with about 80% of it being converted to acetone, which is similarly a CNS depressant, but with a much longer half-life (16–20 h) than alcohol.


Diagnosis and Treatment

CNS depression, hypotension, vomiting, and abdominal pain due to severe gastritis secondary to direct irritation are clinical indications of isopropanol toxicosis, which are comparable to those of ethanol toxicosis. Patients who have ingested isopropanol have an acetone-like odour in their breath (Somerville and Plumlee, 1996). Fluids, correction of acid–base abnormalities, and, if necessary, aided respiration are all part of the supportive treatment (Oehme and Kore, 2006). Isopropanol and acetone can be extracted via dialysis, and 4-methylpyrazole can prevent isopropanol from converting to acetone.


Isopropanol Uses

Isopropyl alcohol was used in 45,000 metric tonnes in the United States in 1990, largely as a solvent for coatings and industrial processes. 5400 metric tonnes were used for household and personal care items in that year. Because of its low toxicity, isopropyl alcohol is particularly popular in pharmaceutical applications. As a chemical intermediate, some isopropyl alcohol is used. While isopropyl alcohol can be converted to acetone, the cumene method has a larger effect.

Let us look at the isopropanol uses across various industries here:

Medical

A 60–70% solution of isopropyl alcohol or ethanol in water is often found in rubbing alcohol, hand sanitizer, and disinfection pads. Water is required to open bacterial cell membrane pores, which serve as a channel for isopropyl alcohol. As a hand sanitizer, 75% of solution in water can be used. Isopropyl alcohol is used as a water-drying aid to prevent otitis externa, also known as swimmer's ear.

Automotive

Isopropyl alcohol is a primary ingredient in fuel additives for "gas dryers." Water is an issue in fuel tanks in large quantities because it separates from the gasoline and can freeze in the supply lines at low temperatures. Alcohol does not remove water from gasoline, although it does help to solubilize it. When water is soluble, it no longer accumulates in supply lines and freezes, but instead dissolve within the fuel itself, presenting a lower risk than insoluble water. As a windshield or door lock de icer, isopropyl alcohol is widely available in aerosol cans.


Did You Know?

Isopropyl alcohol vapour is denser than air and flammable, ranging from 2 to 12.7% flammability in air. It should be protected away from heat and open flames. It has been observed that condensing isopropyl alcohol over magnesium produces peroxides, which can explode when concentrated. Isopropyl alcohol irritates the eyes and is a possible allergen. Wearing protective gloves is strongly advised.

FAQs on Isopropanol

1. What is isopropanol, and what is its official IUPAC name?

Isopropanol is a colourless, flammable chemical compound with a strong odour, commonly known as rubbing alcohol. It is the simplest example of a secondary alcohol. Its chemical formula is CH₃CH(OH)CH₃, and its official IUPAC name, as per systematic nomenclature, is propan-2-ol.

2. What are the most common uses of isopropanol in household and industrial applications?

Isopropanol is widely used due to its excellent solvent properties and effectiveness as a disinfectant. Its main applications include:

  • Antiseptic and Disinfectant: A solution of 60-75% isopropanol in water is a key ingredient in rubbing alcohol, hand sanitisers, and disinfectant wipes.
  • Solvent: It is used in industries to dissolve a wide range of non-polar compounds, including oils, gums, and natural resins.
  • Cleaning Agent: It is ideal for cleaning electronic components, glass surfaces, and lenses because it evaporates quickly without leaving a residue.
  • Fuel Additive: It acts as a water-drying agent ('gas dryer') in fuel tanks, preventing water from freezing in fuel lines.

3. How does the chemical structure of isopropanol classify it as a secondary alcohol?

Isopropanol is classified as a secondary (2°) alcohol because the carbon atom that is bonded to the hydroxyl (-OH) group is itself directly attached to two other carbon atoms. In the structure of propan-2-ol, CH₃-CH(OH)-CH₃, the central carbon atom is bonded to the -OH group and two methyl (-CH₃) groups. This structural feature differentiates it from primary alcohols (like 1-propanol) and tertiary alcohols, and directly influences its chemical reactivity.

4. How does isopropanol differ from its structural isomer, 1-propanol?

Isopropanol (propan-2-ol) and 1-propanol are structural isomers with the same molecular formula (C₃H₈O) but different structures and properties. The key difference lies in the position of the hydroxyl (-OH) group:

  • In isopropanol, the -OH group is attached to the second (central) carbon atom, making it a secondary alcohol.
  • In 1-propanol, the -OH group is attached to a terminal (end) carbon atom, making it a primary alcohol.
This difference in structure leads to variations in their boiling points, solvent properties, and chemical reactivity, especially in oxidation reactions.

5. What is the primary industrial method for preparing isopropanol?

The main commercial method for producing isopropanol is the hydration of propene (also known as propylene). This reaction can be carried out in two ways:

  • Indirect Hydration: Propene is reacted with sulfuric acid to form isopropyl sulfates, which are then hydrolysed with steam to yield isopropanol.
  • Direct Hydration: Propene and water are reacted directly at high pressure and temperature over an acidic catalyst.
Both methods efficiently convert the alkene feedstock into the desired secondary alcohol.

6. Why is a 70% isopropanol solution a more effective disinfectant than a 100% pure solution?

A 70% aqueous solution of isopropanol is a more potent disinfectant because water is essential for its mechanism of action against microbes like bacteria. Pure (100%) isopropanol causes the proteins on the outside of a cell to coagulate too quickly. This forms a protective outer layer that prevents the alcohol from penetrating the cell. The presence of water in a 70% solution slows this coagulation process, allowing the isopropanol to enter the cell and denature the critical internal proteins and enzymes, thus effectively killing the microbe.

7. In a laboratory context, why is isopropanol used for DNA precipitation and how does it compare to ethanol for this purpose?

Isopropanol is used in molecular biology to precipitate DNA from an aqueous solution because DNA is insoluble in it. It is often preferred over ethanol for two main reasons:

  • Volume Efficiency: DNA is less soluble in isopropanol than in ethanol, meaning a smaller volume (around 0.6-0.7 volumes) is needed to cause precipitation. This is useful when working with large sample volumes.
  • Salt Precipitation: While both alcohols precipitate DNA, isopropanol is less effective at co-precipitating salts like NaCl, which can sometimes lead to a purer DNA sample. However, the resulting DNA pellet may be less compact and harder to see than one precipitated with ethanol.