What Is Citral Definition Molecular Formula Isomers and Key Uses
Citral (C10H16O) is a pale yellow liquid, and it has a strong lemon-like odour. It is also called 3,7-dimethyl-2, c-octadienal. Citral can not be mixed well with water, which means it is insoluble in water, but it is soluble in ethyl odour (ethanol), Mineral oil, and diethyl ether. It is mainly used in the manufacturing of perfumes and other smelling chemicals. Moreover, citral is a combination or mixture of two different aldehydes with different structures and the same molecular formula. Citral is known for its acceptable, distinct, and lemon-like pleasant smell. Mehylionene and lonone are made from citral and used in perfumery. It can be synthesized from myrcene, and ionene can be converted into synthetic Vitamin A.
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Properties of Citral
Two compounds are double bond isomers.
There are two types of citrals, citral A is E-isomer, and citral B is Z-isomer. Isomer geraniol has a lemon-like smell, and isomer neral has a less intense and sweeter lemon-like smell.
Physical Properties of Citral
Citral is a clear yellow-coloured fluid with a lemon-like fragrance.
The density of citral is 0.9 g/cm³.
Less dense than water.
Insoluble in water.
The melting point of citral is <-10°C
Citral is not persistent to alkanes and strong acid
When heated to decomposition, it emits acrid smoke and irritating fumes.
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Citral Uses
Citral is commonly used in beverages, foods, cosmetics, and other products. Its possible carcinogenic effects were investigated because of its versatile use in many products like citral oil and citral good scents. Moreover, in the investigation, two rats – one male and one female were used. Male mice were subjected to microencapsulated pure citral (500-4000 ppm) in food for 14 weeks or two years. Well, researchers could not find any proven data of carcinogenic activity of pure citral in mice and rats (According to anonymous data).
Well, citral is used as the flavouring agent and natural additive ingredient in foods, beverages, and cosmetics. Citral has properties of the acidic environment and chemical instability; hence its application domains are limited. Well, degradation of citral has been an industrial issue for many years, and it is a challenging task for ten years. In addition, the ways of citral degradation retarding are also some of the reasons for the limited use of o citral. Decreasing temperature, removing oxygen, and neutralizing pH are some ways of the citral degradation retarding process. The antioxidation process can prevent citral degradation, but this process is not available for non-commercially extensive extraction and costly processes. Moreover, antioxidants are not always suited as some antioxidants may add undesirable colour and taste to food products. Citral is also used as ingredients of citral sigma products that are very popular.
Citral Oil
Citral is a natural substance that can be obtained from plant oils. Lemongrass oil contains 75 to 80 % citral that may be isolated through the distillation process. Some other natural sources include verbena oil and citronella oil. Citral can be obtained from myrcene. It is generally found in the peel of the orange. Because of their intense aroma and flavour are used in beverages, perfumes, cosmetics, and food. Essential oils that present citral shows antifungal, antimicrobial, antiparasitic features that make it a natural preservative.
Citral Medicinal Uses
Citral has beautiful features like incense, anti-inflammatory, antibacterial, etc. It can also be used as a bug repellent. Here are some properties described that add values of citral to be used in medicines.
Antibacterial: Citral has strong antimicrobial properties in addition to fragrance. A study of Letters In Applied Microbiology declared that citral shows antimicrobial activity against gram-negative and gram-positive bacteria and fungus.
Anti-Inflammatory: Citral may also possess anti-inflammatory properties. A 2017 study on mice found that citral showed a significant decrease in TNF-α (Tumor Necrosis Factor-alpha) levels in tests demonstrating anti-inflammatory activity.
Bug-Repellent: Citral is one of the active components of citronella oil, a common ingredient used in insect repellents and citronella candles. Citronella has been registered as a gentle, plant-based insect repellent in the United States since 1948. Some evidence suggests that citral and the other active compounds in citronella interfere with mosquito olfactory receptors.
FAQs on Citral Structure Properties and Chemical Behavior
1. What is citral in chemistry?
Citral is a naturally occurring monoterpene aldehyde with the molecular formula C10H16O that gives a strong lemon-like aroma. It is an unsaturated aliphatic aldehyde found in essential oils such as lemongrass and lemon myrtle oil. Chemically, citral consists of two geometric isomers (geranial and neral) and contains:
- An aldehyde functional group (–CHO)
- Two carbon–carbon double bonds (C=C)
- A 10‑carbon terpene backbone
2. What is the chemical formula and structure of citral?
The chemical formula of citral is C10H16O, and it is an acyclic unsaturated aldehyde. Its IUPAC name is 3,7-dimethyl-2,6-octadienal. Key structural features include:
- A terminal –CHO (aldehyde) group
- Two C=C double bonds at positions 2 and 6
- Methyl (–CH3) substituents on the carbon chain
3. What are the isomers of citral?
Citral exists as two geometric (E/Z) isomers: geranial (E‑citral) and neral (Z‑citral). These isomers differ in the configuration around one of the carbon–carbon double bonds.
- Geranial (trans or E form): stronger lemon odor, more thermodynamically stable
- Neral (cis or Z form): slightly milder aroma
4. What functional group is present in citral?
Citral contains an aldehyde functional group (–CHO) along with two alkene (C=C) groups. The aldehyde group is responsible for many of its characteristic chemical reactions, such as oxidation and nucleophilic addition. Because one double bond is conjugated with the carbonyl group, citral behaves as an α,β-unsaturated aldehyde, making it reactive in addition and condensation reactions.
5. How is citral obtained or synthesized?
Citral is primarily obtained from natural essential oils or synthesized through terpene chemistry reactions. It is commonly extracted from:
- Lemongrass oil
- Lemon myrtle oil
- Litsea cubeba oil
6. What are the physical properties of citral?
Citral is a yellowish liquid with a strong lemon odor and moderate volatility. Its important physical properties include:
- Molecular formula: C10H16O
- Molar mass: 152.24 g·mol-1
- Boiling point: approximately 229°C
- Low solubility in water but soluble in organic solvents like ethanol
7. What chemical reactions does citral undergo?
Citral undergoes typical reactions of aldehydes and alkenes due to its functional groups. Common reactions include:
- Oxidation: aldehyde group can be oxidized to a carboxylic acid
- Reduction: can be reduced to the corresponding alcohol (e.g., geraniol)
- Nucleophilic addition: addition at the carbonyl carbon
- Electrophilic addition: reactions at the C=C double bonds
8. What is the difference between citral and geraniol?
The main difference between citral and geraniol is that citral is an aldehyde while geraniol is an alcohol. Chemically:
- Citral: contains a –CHO group; formula C10H16O
- Geraniol: contains a –OH group; formula C10H18O
9. Why is citral classified as an α,β-unsaturated aldehyde?
Citral is classified as an α,β-unsaturated aldehyde because one of its C=C double bonds is directly conjugated with the carbonyl (C=O) group. In this structure:
- The carbon adjacent to the carbonyl is the α-carbon
- The next carbon in the double bond is the β-carbon
10. What are the uses of citral in chemistry and industry?
Citral is widely used as a fragrance compound and as a starting material in organic synthesis. Major uses include:
- Flavoring and fragrance in perfumes and food products
- Intermediate in the synthesis of vitamin A
- Production of ionones and other aroma chemicals
- Research in natural product and terpene chemistry
