What Is Lactic Acid Definition Formula Formation Reactions and Uses
Lactic acid, also known as lactate, is a chemical byproduct of anaerobic respiration. It refers to a process where cells produce energy without having oxygen around. Lactic acid gets produced in yoghurt by some bacteria. It is also present in your gut and blood. Your muscles and red blood cells often deposit the lactate into your blood. So, lactic acid is an organic one. It’s a chiral molecule, and it has two optical isomers, which are L-lactic acid and D-lactic acid. The presence of a carboxyl group adjacent to the hydroxyl group makes lactic acid an alpha-hydroxy acid. In this article, you can learn about lactic acid structure, its definition, uses, and sources.
What is Lactic Acid?
Lactic acid is one of the organic acids. The chemical formula of the lactic acid is C3H6O3. It has two optical isomers, Levo and Dextro, making itself a chiral molecule. L-isomers are commonly present among living organisms. The lactic acid has a significant part in various biochemical processes. It gets produced by the muscles during intense activity.
Lactic acid is soluble in water. It looks white in its solid-state and becomes colourless in the liquid state. Milk acid is another name of lactic acid. When lactose or milk sugar undergoes fermentation, the lactic acid gets produced. You can also find it in other dairy products like cottage cheese, yoghurt, etc.
Just so you know, a Swedish chemist, named Carl Wilhelm Scheele, isolated the lactic acid from milk for the first time in 1780. Also, the soluble salt of lactic acid, such as calcium lactate can act as a source of calcium. The PH of 1 mM of lactic acid is nearly 3.51. You can learn more about lactic acid as below.
Structure of Lactic Acid
Below you can find the structural representation of lactic acid or C3H6O3.
(Images to be added soon)
The extended formula of lactic acid is CH3CH(OH)CO2H, and it has a molar mass of 90.08 g/mol. Since a single carbon houses hydroxyl group (-OH) and carboxylic group (-COOH), the molecule gets classified as alpha-hydroxy acid. The central carbon is a chiral as it appears and the other two substituent groups are a hydrogen atom on a methyl group (-CH3). It results in two different structures: L-lactic acid (+) and D-lactic acid (-).
Properties of Lactic Acid
Lactic acid is colorless or yellow syrupy, during its liquid state. In solid form, you can find it in the white powder.
The molecular weight or molar mass of lactic acid is 90.08 g/mol. And it’s PH level is 3.51 per 1 mM of lactic acid.
The melting point of lactic acid is 530 Celsius, and the boiling point is 1220 Celsius. It is soluble in water and ethanol.
Lactic acid is corrosive to any metals and tissue. Thus, overuse and overconsumption of the lactic acid can come with severe side effects.
Uses of Lactic Acid
There are numerous lactic acid uses, and the first thing to note is that your body can produce lactic acid on its own. But, there is a significant requirement for industrially produced lactic acid. It can get formed using a synthetic process or fermentation. The latter involves usage of nutrients like amino acids, vitamins, peptides, glucose, and salt. These nutrients get combined with microbes, which further uses nutrients to give out lactic acid.
Once the lactic acid is ready, it can be used for various purposes as below.
Personal products and healthcare products
Food preservatives
Dairy products, like yoghurt
Cleaning, laundry, and dishwashing products
Paint and coating additives
Furniture care products
Textile dyeing and leather tanning
Pharmaceuticals
Applications of Acids and Basic Substances
Due to the different properties of acids and bases, they have a significant role in real-life applications. Some of the applications are-
Applications of Acid Substances
Citric acid is a key ingredient in lemons and oranges. Acids can also be utilized to preserve food.
Sulfuric acid is widely used in car batteries, which are commonly used to start the engines of automobiles.
Acids are used in the industrial production of explosives, dyes, and fertilizers.
Phosphoric acid is one of the key ingredients in many soft drinks.
Vinegar is a diluted form of acetic acid and it features several home applications like preserving food, etc.
Applications of Basic Substances
Ammonium hydroxide is one of the most important reagents used in laboratories.
Any extra acidity in the ground (soil), could be neutralized by utilizing slaked lime.
Ca(OH)2 (also known as slaked lime or calcium hydroxide) is used to make dust which is used for bleaching powder.
Calcium Hydroxide is used to make dry mixes which are utilized in design or artwork.
The production of soap and paper requires the utilization of salt (sodium hydroxide).
NaOH is utilized in the making of rayon.
Magnesium hydroxide(also referred to as milk of magnesia) is usually used as a laxative and it also decreases any extra acidity in a human's stomach. This property qualifies it to be an antacid.
FAQs on Lactic Acid Structure Properties Preparation and Applications
1. What is lactic acid?
Lactic acid is an organic acid with the chemical formula C3H6O3 that contains both a hydroxyl (–OH) and a carboxyl (–COOH) group. It is classified as an alpha-hydroxy acid (AHA) because the –OH group is attached to the carbon adjacent to the carboxyl group. Lactic acid is commonly produced during anaerobic respiration and is widely used in food, pharmaceuticals, and biodegradable plastics.
2. What is the chemical formula and structure of lactic acid?
The chemical formula of lactic acid is C3H6O3, and its structural formula is CH3–CH(OH)–COOH. The molecule contains:
- A carboxyl group (–COOH) responsible for its acidic properties.
- A hydroxyl group (–OH) on the second carbon.
- A chiral carbon atom, giving rise to optical isomerism.
3. Why is lactic acid called an alpha-hydroxy acid?
Lactic acid is called an alpha-hydroxy acid (AHA) because it has a hydroxyl (–OH) group attached to the alpha carbon next to the carboxyl (–COOH) group. In organic chemistry:
- The carbon adjacent to the –COOH group is called the alpha (α) carbon.
- In lactic acid, this carbon carries the –OH group.
4. How is lactic acid produced in the body?
Lactic acid is produced in the body during anaerobic respiration when glucose is broken down without sufficient oxygen. The simplified reaction is: C6H12O6(aq) → 2C3H6O3(aq)
- Glucose undergoes glycolysis to form pyruvate.
- Pyruvate is reduced to lactic acid in low-oxygen conditions.
- This process regenerates NAD+, allowing glycolysis to continue.
5. What is the difference between lactic acid and lactate?
Lactic acid is the protonated form (C3H6O3), while lactate is its conjugate base (C3H5O3−) formed after losing a proton (H+). The equilibrium is: C3H6O3(aq) ⇌ C3H5O3−(aq) + H+(aq)
- Lactic acid predominates at low pH.
- Lactate predominates at physiological pH (~7.4).
6. Is lactic acid a strong or weak acid?
Lactic acid is a weak acid because it only partially ionizes in aqueous solution. Its acid dissociation can be written as: C3H6O3(aq) ⇌ C3H5O3−(aq) + H+(aq)
- It has a pKa of about 3.86 at 25°C.
- Partial ionization is characteristic of weak carboxylic acids.
7. What are the optical isomers of lactic acid?
Lactic acid has two optical isomers: L-(+)-lactic acid and D-(−)-lactic acid. This occurs because:
- The second carbon atom is a chiral center.
- It is attached to four different groups (–H, –OH, –CH3, –COOH).
8. How does lactic acid react with bases?
Lactic acid reacts with bases in a neutralization reaction to form lactate salts and water. For example, with sodium hydroxide: C3H6O3(aq) + NaOH(aq) → C3H5O3Na(aq) + H2O(l)
- The –COOH group donates a proton (H+).
- A lactate salt, such as sodium lactate, is formed.
9. What is the molar mass of lactic acid?
The molar mass of lactic acid (C3H6O3) is approximately 90.08 g·mol−1. It is calculated as:
- Carbon: 3 × 12.01 = 36.03 g·mol−1
- Hydrogen: 6 × 1.008 = 6.048 g·mol−1
- Oxygen: 3 × 16.00 = 48.00 g·mol−1
10. What are the main uses of lactic acid in chemistry and industry?
Lactic acid is widely used in food, pharmaceuticals, and polymer chemistry due to its acidic and biodegradable properties. Major uses include:
- Food preservative and acidity regulator in fermented products.
- Production of polylactic acid (PLA), a biodegradable polymer.
- pH regulator in cosmetics and skincare (as an AHA).
- Preparation of lactate salts in pharmaceuticals.
