Question

Give an equation for the complete hydrogenation of trilinolein using an excess of hydrogen. Name the product and predict approximate melting points for the starting material and the product.

Short answer

Hydrogenation is a chemical reaction between molecular hydrogen and another compound or element usually in the presence of a catalyst such as nickel, palladium, or platinum. This type of reaction is an example of alkene addition, and two hydrogen atoms are added across the double bond of an alkene which results in formation of a saturated alkane.

Step-by-step solution

Step-1. Hydrogenation reaction:

Hydrogenation is a chemical reaction between molecular hydrogen and another compound or element usually in the presence of a catalyst such as nickel, palladium, or platinum. This type of reaction is an example of alkene addition, and two hydrogen atoms are added across the double bond of an alkene which results in formation of a saturated alkane.

Step-2. Hydrogenation of trilinolein:

Trilinolein on hydrogenation with excess hydrogen in presence of nickel catalyst results in the formation of tristearin which is solid at room temperature. Melting point of trilinolein is less than -4⁰C and it is liquid at room temperature. Melting point of tristearin is 72⁰C. Melting point of trilinolein is lower than triolein because more double bonds lower the melting point. Sources differ on the melting point of trilinolein, ranging from -17⁰C to -43⁰C.

Hydrogenation of trilinolein