Hydrogenation of Alkenes

1
Hydrogenation of Alkenes
Processed foods may contain partially
hydrogenated vegetable oils
2
Why Hydrogenated Vegetable Oils?

• Longer shelf life alkenes undergo air
  oxidation.
• Convert liquid fats into solid fats.
• Why not just use animal fats (more saturated)?
• Vegetarian
• No cholesterol in plant products

3
Air Oxidation of Oils
Oxidation
O2
Aldehyde products can be further oxidized to
carboxylic acids. Oxidation of oils generates
rancid odor.
4
Saturation or Unsaturation Affects Melting Point
Elaidic acid Melting point 44 C
Oleic acid Melting point 13 C
Stearic acid Melting point 70 C
5
Partially Hydrogenated Vegetable Oils Yields
Trans-Fats
Trans- alkene
Hydrogenation
Pt
H2
Cis-alkenes
Olefin isomerization occurs under the reduction
conditions
Trans-fats increase levels of low-density
lipoproteins (LDLs) and decrease levels of high
density lipoproteins (HDLs)
6
Omega-3 and Omega-6 Fatty Acids are
Polyunsaturated
Recommended omega-6/omega-3 ratio 41. Most
American diets gt101
Why found in cold water fish?
Omega-3 fatty acids
Linolenic acid Canola, flaxseed oils
Eicosapentaenoic acid (EPA) Cold water fish
salmon, herring, sardines
Omega-6 fatty acids
Linoleic acid Vegetable oils
Arachidonic acid Animal sources meat, eggs,
dairy