The key difference between limonene and D limonene is that limonene is a cyclic monoterpene whereas D limonene is the D isomer of limonene.
Limonene is an organic compound. It shows stereoisomerism. This means there are two isomers of limonene as L isomer and D isomer. Among these two isomers, D limonene is the most common and abundant isomer.
CONTENTS
1. Overview and Key Difference
2. What is Limonene
3. What is D Limonene
4. Side by Side Comparison – Limonene vs D Limonene in Tabular Form
5. Summary
What is Limonene?
Limonene is a cyclic monoterpene having the chemical formula C10H16. It occurs as a colourless liquid that can be categorized as an aliphatic hydrocarbon. This compound is the major substance in the oil of citrus fruit peels. This compound shows stereoisomerism; there are two isomers as D limonene and L limonene. Among these two isomers, D limonene is the most commonly occurring isomer in nature. This D isomer can be found in oranges as the fragrance, so it is important as a flavouring agent in food manufacturing. Moreover, this compound is useful in chemical synthesis reactions as a precursor.
D isomer is the abundant isomer of limonene. L isomer is less common and we can find it in mint oils. L limonene has a piny and turpentine-like odour. It is a volatile monoterpene that we can find in resins of conifers.
Figure 01: Chemical Structure of Limonene
The name limonene originates from the word “lemon”. Limonene is a chiral compound. The principal industrial source of limonene is citrus fruits which contain D limonene. It is the R isomer of the racemic mixture of limonene. The racemic mixture of limonene is named as dipentene. There are two methods of obtaining D limonene: centrifugal separation and steam distillation.
When considering the properties of limonene, it is relatively stable and we can distil it without it undergoing decomposition. However, limonene easily cracks at elevated temperatures, forming isoprene. Moreover, limonene easily oxidizes in moist air producing carveol, carvone and limonene oxide. In the presence of sulfur, limonene undergoes dehydrogenation and forms p-cymene.
What is D Limonene?
D limonene is the D isomer of limonene molecule. It is the most common and stable isomer of limonene. The major source of D limonene is citrus fruit. It is a common and major component in the aromatic scents and resins that are characteristic of numerous coniferous and broadleaved trees.
D limonene can be extracted from citrus fruits industrially via centrifugal separation and steam distillation. D limonene occurs as a colourless or pale yellow liquid that has the odour of orange. Therefore, it is a common additive in the food industry as a flavouring agent. It is also important as a dietary supplement and as a fragrance in cosmetic productions. Moreover, this substance is important in the food industry and in the production of some medicine. D limonene is useful as a botanical insecticide as well.
What is the Difference Between Limonene and D Limonene?
Limonene is a cyclic monoterpene compound. It shows stereoisomerism; there are two isomers of limonene as the D isomer and the L isomer. The key difference between limonene and D limonene is that limonene is a cyclic monoterpene whereas D limonene is the D isomer of limonene.
Below infographic lists more differences between limonene and D limonene.
Summary – Limonene vs D Limonene
Limonene is a cyclic monoterpene compound. It shows stereoisomerism; there are two isomers of limonene as the D isomer and the L isomer. The key difference between limonene and D limonene is that limonene is a cyclic monoterpene whereas D limonene is the D isomer of limonene.
Reference:
1. “Limonene.” Wikipedia, Wikimedia Foundation, 4 Sept. 2020, Available here.
Image Courtesy:
1. “Limonene-2D-skeletal” By Original file:Limonene-2D-skeletal.png by User:Benjah-bmm27derivative work: user:Karlhahn – Limonene-2D-skeletal.png (Public Domain) via Commons Wikimedia