Low Molecular Weight Esters - Carboxyl / Alfa Chemistry

Introduction

An ester is a chemical compound derived from an acid (organic or inorganic) in which at least one -OH (hydroxyl group) is replaced by an -O-alkyl (alkoxy group) , as in the substitution reaction of a carboxylic acid and an alcohol and it is generally written RCOOR' or RCO2R'.

Fig 1. Structure of esters

Physical Properties of Esters

Ester molecules are polar but have no hydrogen atom attached directly to an oxygen atom. They are therefore incapable of engaging in intermolecular hydrogen bonding with one another and thus have considerably lower boiling points than their isomeric carboxylic acids counterparts. Because ester molecules can engage in hydrogen bonding with water molecules, however, esters of low molar mass are somewhat soluble in water. Table 1 lists the physical properties of some common esters.

Condensed Structural Formula	Molar Mass	Melting Point	Boiling Point	Aroma
HCOOCH₃	60	-99°C	32°C
HCOOCH₂CH₃	74	-80°C	54°C	rum
CH₃COOCH₃	74	-98°C	57°C
CH₃COOCH₂CH₃	88	-84°C	77°C
CH₃CH₂CH₂COOCH₃	102	-85°C	102°C	apple
CH₃CH₂CH₂COOCH₂CH₃	116	-101°C	121°C	pineapple
CH₃COO(CH₂)₄CH₃	130	-71°C	148°C	pear
CH₃COOCH₂CH₂CH(CH₃)₂	130	-79°C	142°C	banana
CH₃COOCH₂C₆H₅	150	-51°C	215°C	jasmine
CH₃CH₂CH₂COO(CH₂)₄CH₃	158	-73°C	185°C	apricot
CH₃COO(CH₂)₇CH₃	172	-39°C	210°C	orange

Table 1. Physical properties of some common esters

Esters are ubiquitous. Esters are typically fragrant, and those with low enough molecular weights to be volatile are commonly used as perfumes and are found in essential oils and pheromones. Common esters and their odors are listed below:

Table 2. Tables of esters and their smells

Applications of Low Molecular Weight Esters

In Personal Care Market

In recent years, there has been a rising demand for esters in the personal care space, where they can stand in for traditional petroleum ingredients. In personal care products, esters can function as emollients, solvents, thickening agents, surfactants and fragrances.

Fig. 2 Application in personal care products

In Food Market

The food industry has long understood the value of esters and has used, and continues to use, them in a variety of products. Esters can help enhance flavor and are especially useful as an emulsifier. Emulsifiers are surfactants, meaning they reduce surface tension between two immiscible liquids, such as water and oil, thereby stabilizing the mixture. Esters can also improve the texture of many food products, including low-fat liquids which may lack enough viscosity without the standard amount of fat.

Fig. 3 Application in food

In Industry Field

Low molecular weight esters can be used in all areas of industry. For example, low molecular weight esters can be used as potential low-temperature drilling fluids for ice coring.

From the desired-density point of view, ethyl butyrate and n-propyl propionate best meet cold-ice drilling requirements. The viscosities of these two chemicals are the lowest among studied FAEs, and do not exceed 4mPas at temperatures down to –60°C. Both are highly volatile substances and essentially insoluble in water.

Fig. 4 Application in low-temperature drilling fluids for ice coring

Besides, low molecular weight esters can be used in many other fields like pheromones, plastic, photoresist, pharmaceuticals areas, etc.

Alfa Chemistry provides various of low molecular weight esters to our customers from grams to kilograms. We can also customize synthesis according to customers' requirements. Please feel free to contact us for more information.

Reference:

Huiwen XU, Lili HAN, Pinlu CAO, etc. Low-molecular-weight, fatty-acid esters as potential low-temperature drilling fluids for ice coring. Annals of Glaciology. 2014, 55(68):39-43.