Cis-3-Hexenal

Cis-3-Hexenal, also known as (Z)-3-hexenal and leaf aldehyde, is an organic compound with the formula C₆H₁₀O. It is a colorless liquid that is an important aroma compound found in nature. Cis-3-Hexenal has a distinctive fresh, green, grassy odor and is a significant contributor to the aroma of green leaves, unripe fruits, and at certain concentrations, it imparts a pleasant odor reminiscent of freshly cut grass. Due to its potent odor, it is used in very low concentrations in perfumery and flavors.

Structure and Properties

Cis-3-Hexenal is an aldehyde and a monounsaturated compound, with the double bond in the cis configuration, which significantly influences its aroma and chemical properties. The molecule consists of a six-carbon chain with an aldehyde group at one end. The cis configuration of the double bond at the third carbon atom is crucial for its characteristic odor.

Biosynthesis

In plants, cis-3-Hexenal is formed from linolenic acid via the lipoxygenase pathway. The enzyme lipoxygenase adds oxygen to linolenic acid, which is then converted by other enzymes into cis-3-Hexenal. This compound is often released when plant tissues are damaged, as part of the plant's defense mechanism against herbivores.

Occurrence

Cis-3-Hexenal is widely distributed in nature. It is found in the volatile components of many fruits and vegetables, including tomatoes, apples, and green peppers. It is also a significant component of the aroma of freshly cut grass and leaves. The compound plays a crucial role in the flavor profile of many fresh foods and is valued for its contribution to the "green" notes of their aroma.

Uses

Due to its distinctive smell, cis-3-Hexenal is used in the flavor and fragrance industry. It is added to food products to impart a fresh, green aroma and is used in perfumery to create natural green, grassy scents. However, due to its high volatility and reactivity, its use must be carefully controlled to avoid undesirable off-flavors and aromas.

Safety and Toxicology

Cis-3-Hexenal is generally considered safe for use in flavors and fragrances. However, like many aldehydes, it can be irritating to the skin and eyes in high concentrations. Proper handling and dilution are necessary to mitigate these effects.