Trans Fatty Acid Structure:Detailed Explanations

The amount of trans fatty acid, found naturally is very small. The processed foods contain a large amount of trans fatty acid. In the article we see trans fatty acid structure and other facts about it.

Trans fatty acids are one type of unsaturated fatty acids with Carbon – Carbon double bond. The structure is a long hydrocarbon chain. In the trans fatty acid structure there is a Carboxylic group (-COOH) at the end of the hydrocarbon chain.

The fatty acids that are not saturated, are classified into two groups. In one type of the fatty acids, there one double bond present, these are called monounsaturated fatty acid. In another type of fatty acids, there present more than one double bond in the hydrocarbon chain. These are called polyunsaturated fatty acids.

In the trans fatty acid structure the word ‘trans’ identifies the configuration of the hydrocarbon chain. It means the Hydrogen atoms on the double bond are in opposite direction with respect to each other. For the pi bond present in the hydrocarbon chain, the structure is in locked position.

Trans fatty acids are isomer of cis fatty acids. The trans fatty acids are less common with respect to the cis fatty acids in nature.

 In the fatty acid chain, the carbon atoms of the carbon – carbon double are sp2 hybridized. So they remain in same plane. For the trans bond present in the fatty acid chain; the trans fatty acid has a straight chain structure. The chain can’t bend much.

Most of the fatty acids have even number of Carbon atoms in the hydrocarbon chain. Some of the fatty acids have odd number of Carbon atoms in the fatty acid chain. These are called odd chained fatty acids.

Most of the fatty acids have no branch in the hydrocarbon chain which we find naturally. In the trans fatty acid structure, hydrocarbon chain has a carboxyl group (-COOH) at one end of the chain. In another end of the chain there is a methyl group (-CH3).

In general for numbering of the hydrocarbon chain of the trans fatty acid; the Carbon atom next to the Carboxyl group is pointed as alpha (α) Carbon. So it is the second carbon atom of the chain. Next to the alpha Carbon is called as beta Carbon (β). The last Carbon atom is said to be the omega (Ѡ) Carbon.

The number of the position of the double bond of the trans fatty acid chain is given from which side the carboxyl group is closest. In a fatty acid chain there are 16 Carbon atoms and the double bond is between the 12th carbon (C-12) atom and the 13th carbon atom (C-13). In this case the numbering of the double bond is said to be at C-12.

The sign ∆x,y  is used for showing the position of the double bond at the carbon atoms x and y in the hydrocarbon chain. For example ∆5,8 means that the hydrocarbon chain of the fatty acid contains pi bond between the carbon atoms 5 and 6, and between 8 and 9.

trans fatty acid structure
Trans fatty acid structure

For the straight chain structure of the trans fatty acids, they can form packed structure easily in solid state. This indicates that the trans fatty acids easily convert them into semi-solid form from the oil. Because of this the melting point of the fatty acid is higher.

Trans fatty acid structure are produced from cis fatty acids through isomerization process in hydrogenation. Naturally trans fatty acids occurs in ruminant meat and milk in a small amount. Elaidic acid is a trans fatty acid. It is found in vegetable oil.

Besides these during the heating and frying of oil at high temperature results in the formation of trans fatty acids.

If one take high amount of trans fatty acid containing food, it increases the cholesterol level in the blood which is harmful for our health. It increases the heart problem possibility. In our present day, a huge amount of world population is suffering from obesity problem. Taking foods containing trans fatty acid type unsaturated fats is a reason for it.

Triyasha Mondal

Hi...I am Triyasha Mondal, pursuing M.Sc in Chemistry. I am an enthusiastic learner. My specialization is in physical chemistry. Let's connect through LinkedIn:

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