Lipids - G. Modifications of fats and oils - Hydrogenation

7 important questions on Lipids - G. Modifications of fats and oils - Hydrogenation

What happens in a hydrogenation reaction with as catalyzer nikkel and there is not enough hydrogen, so an incomplete reaction?

It can become a:
  1. positional isomer
  2. cis bond
  3. or a trans bond


1 ad 3 can also happen combined

If you have 18:1, 9 cis what trans fatty acids can be formed?

Geometrical:
e.g. 18:1, 9c --> 18:1, 9t

and/or

Positional: double bond has been moved to other positions along the carbon chain
e.g. 18:1, 9c --> 18:1, 11t

What are the three possible geometrical TFA isomers of 18:2, 9c, 12c?

18:2, 9c, 12t and 18:2, 9t, 12c and 18:2, 9t, 12t
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What is the effect of hydrogenation on the melting point?

The melting point goes up since you have less poly unsaturated fatty acids. Or you changed there structure.

What are the factors that effect hydrogenation?

  • Temperature
  • Hydrogen gas pressure
  • Catalyst activity and concentration
  • Agitation
  • Time

Does an increase in hydrogen pressure will more likely increase or decrease the formation of trans fatty acids

Decrease. If there is more hydrogen, the chance that the catalyst does not receive enough hydrogen during the process is low.

What is selectivity during hydrogenation?

It tells you something about how fast the reaction is taking place.

S(3,2)=K(3)/K(2)=2
Meaning the selectivity is 2 which means that the reaction of 3 double bonds to 2 double bonds is twice as fast at the reaction form 2 double bonds to 1 double bond.

K3 needs to be as high as possible

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