Cis-3-hexenol (C6H12O) is a colorless, oily, six-carbon alcohol. This organic compound is widely recognized for its strong, fresh, and green aroma, playing a significant role in the natural world and various industries.
The Distinctive “Green” Scent
The aroma of cis-3-hexenol is intensely green, reminiscent of freshly cut grass, green leaves, or raw vegetables. This characteristic scent has earned it common names like “leaf alcohol” or “green leaf volatile” (GLV). The “cis” isomer is responsible for this specific scent profile.
This compound contributes a fresh, grassy, and sometimes herbaceous note to fragrances. It can also have a slight caramellic and fruity nuance. The perception of this odor can be influenced by genetic variations in human odor receptors.
While cis-3-hexenol provides a distinct green scent, its related aldehyde, cis-3-hexenal, has an even stronger, similar smell. Cis-3-hexenal is less stable and can isomerize into trans-2-hexenal. Cis-3-hexenol’s unique structure delivers this fresh, natural green effect.
Natural Occurrence and Biological Role
Cis-3-hexenol is widely distributed in nature, found in small amounts in most plants. It is prevalent in green leaves, various fruits such as apples, apricots, strawberries, and melons, and vegetables like corn, pumpkin, and tomatoes. It is also present in numerous flowers, including gardenia and lilac, as well as in mint oils and tea.
This compound plays a significant biological role in plants, primarily as a signaling molecule. When plant tissues are damaged, such as by cutting grass or insect feeding, cis-3-hexenol is rapidly released. This release is part of a defense mechanism, alerting nearby plants to threats and stimulating their defense responses.
Cis-3-hexenol and its derivatives are involved in plant-insect interactions. They can attract predatory insects, which helps plants by drawing in the natural enemies of herbivores. Conversely, these volatiles can repel certain pests, such as weevils, while attracting others like male scarab beetles. The compound can also induce the expression of defense genes in plants, further contributing to plant resilience.
Applications in Industry
Cis-3-hexenol is widely used in the fragrance industry for its fresh, green, and grassy aroma. It is a common ingredient in perfumes, colognes, and household products like air fresheners, detergents, and soaps. It adds a natural, leafy, and sometimes slightly floral note, suitable for creating scents that evoke the outdoors or fresh botanical themes. It is valued for providing refreshing top notes in delicate floral fragrances, such as lily of the valley and lilac.
In the food and beverage industry, cis-3-hexenol serves as a flavor additive. It enhances or replicates natural green, fruity, or vegetable flavors in products like fruit-flavored drinks, candies, baked goods, and green tea. Its fresh, green character makes it a versatile component in flavor formulations.
Regulatory bodies recognize cis-3-hexenol as safe (GRAS) for its approved uses in fragrances and food. The Flavor and Extract Manufacturers Association (FEMA) has assigned it FEMA number 2563. Safety assessments conclude it does not pose a concern for skin sensitization when used in fragrances.