Propyl hexanoate (C₉H₁₈O₂), also known as propyl caproate, is an

ester In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...

formed by the reaction of

propanol There are two isomers of propanol. * 1-Propanol, ''n''-propanol, or propan-1-ol: CH3CH2CH2OH, the most common meaning *2-Propanol, isopropyl alcohol, isopropanol, or propan-2-ol: (CH3)2CHOH See also * Propanal (propionaldehyde) differs in spel ...

with

hexanoic acid Caproic acid, also known as hexanoic acid, is the carboxylic acid derived from hexane with the chemical formula . It is a colorless oily liquid with a fatty, cheesy, waxy odor resembling that of goats or other barnyard animals. It is a fatty acid ...

. Although it is a completely different ester, propyl hexanoate shares the same chemical formula with methyl octanoate, ethyl heptanoate, butyl pentanoate, etc. because they all have the same total carbon chain length. The scent of this ester can be described as that of

blackberries BlackBerry is a discontinued brand of handheld devices and related mobile services, originally developed and maintained by the Canadian company Research In Motion (RIM, later known as BlackBerry Limited) until 2016. The first BlackBerry device ...

pineapple The pineapple (''Ananas comosus'') is a Tropical vegetation, tropical plant with an edible fruit; it is the most economically significant plant in the family Bromeliaceae. The pineapple is indigenous to South America, where it has been culti ...

cheese Cheese is a type of dairy product produced in a range of flavors, textures, and forms by coagulation of the milk protein casein. It comprises proteins and fat from milk (usually the milk of cows, buffalo, goats or sheep). During prod ...

wine Wine is an alcoholic drink made from Fermentation in winemaking, fermented fruit. Yeast in winemaking, Yeast consumes the sugar in the fruit and converts it to ethanol and carbon dioxide, releasing heat in the process. Wine is most often made f ...

Properties

Due to the length of the carbon chain in this molecule, there are only minor

van der Waals forces In molecular physics and chemistry, the van der Waals force (sometimes van der Waals' force) is a distance-dependent interaction between atoms or molecules. Unlike ionic or covalent bonds, these attractions do not result from a chemical ele ...

acting upon it, which is why propyl hexanoate appears as a liquid and not a solid. Dipole-dipole forces are present because of the polar covalent bonds between carbon and oxygen, while

hydrogen bonding In chemistry, a hydrogen bond (H-bond) is a specific type of molecular interaction that exhibits partial covalent character and cannot be described as a purely electrostatic force. It occurs when a hydrogen (H) atom, Covalent bond, covalently b ...

only occurs with other molecules that can hydrogen bond.

Preparation

Propyl hexanoate is formed by the

condensation reaction In organic chemistry, a condensation reaction is a type of chemical reaction in which two molecules are combined to form a single molecule, usually with the loss of a small molecule such as water. If water is lost, the reaction is also known as a ...

(

esterification In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...

) of propanol and hexanoic acid. The hydroxyl group from the propanol reacts with the hydroxyl group from the hexanoic acid to produce water and leave an oxygen that the parent acid and alcohol chains bond to, creating the ester. For this reaction to occur, it requires an acid

catalyst Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...

, such as concentrated

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...

, and heat. The esterification process can also be reversed (

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...

) to get propanol and hexanoic acid back from propyl hexanoate. This reaction occurs between the ester and water in the presence of a dilute acid catalyst and heat.

Uses

Propyl hexanoate, being an ester, is generally used for replicating the scents or flavors of fruit such as blackberry and pineapple, then is added to things such as food or perfume. It also has the use as a solvent for polar

organic compounds Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

.Hughes, A. (2003)
Uses of Esters
''The Chemistry of Esters''

References

Caproate esters Propyl esters