Lipids
• Naturally occurring materials that preferentially extract into
nonpolar organic solvents
• Includes fats, oils, waxes, some vitamins and hormones, some
components of membrane
• General types: esters (“saponifiable”) and those that can’t be
hydrolyzed
O
H2C O C R
O
HC O C R'
O
H2C O C R"
Triacylglycerol
(R, R', R" = C11 - C19 chains)
H
H
HO
Cholesterol
Fats and Oils
• Animal and vegetable fats are triacylglycerols
– triesters of glycerol with three long-chain carboxylic acids
• Saponification of a fat or oil with (reaction with aqueous NaOH)
yields glycerol and three fatty acids
• Nearly all have even number of C in unbranched chain of fatty acid
• Unsaturated Z (cis) geometry and have lower MP than saturated
counterparts
Saponification (L. sapo, soap). Soaps are the sodium or potassium salts of fatty acids formed
from hydrolysis of fats or oils under basic conditions.
O
Na
O
H2C OH
H2C O C R
O
HC O C R'
O C R
NaOH
O
HC OH
+
Na
O C R'
O
H2C O C R"
Triacylglycerol
H2C OH
Glycerol
O
Na
O C R"
Biodiesel
•1895 – diesel engine developed by Rudolf Diesel to operate on fuels
comprised of 12-18 carbons as alternative to use of refined gasolines
of 7-11 carbons
•Biodiesel - simple alkyl (methyl, ethyl, butyl) esters of fatty acids
•Non-toxic, biodegradable and generally lower carbon monoxide and
hydrocarbon emissions than petroleum-based diesel fuels
Lipids: Fats and Oils
Fats and oils are triesters of glycerol. The carboxylic acids that are bonded to glycerol have
long, unbranched R groups and are called fatty acids.
O
H2C OH
H2C O C R
O
H O H
HC O C R'
lipase
O
O
Triacylglycerol
O
HC OH + HO C R + HO C R' + HO C R"
H2C OH
H2C O C R"
O
Three fatty acids containing 12-20 C's are produced
Glycerol
Biodiesel (Transesterification)
O
H2C OH
H2C O C R
O
HC O C R'
O
H2C O C R"
Triacylglycerol
CH3OH
H+ or HO-
O
HC OH +
H2C OH
Glycerol
CH3O C R +
O
O
CH3O C R' + CH3O C R"
Three fatty acid esters containing 12-20 C's are produced
Biodiesel Procedure
•Place vegetable oil (10 mL) placed in a microwave vessel
•Add 2.91 M KOH/MeoH (1.5 mL) and MeOH (1.5 mL)
•Take note of layers and any color changes
•Cover and tighten vessel and place in in carousel
•Heat at 50 oC for 5 min at 800 W
•Take out vessel after cooling, take note of layers and color
•Transfer to separatory funnel, slowly and cautiously add hydrochloric
acid (20 mL, 6 M)
•Let stand 10 min, draw off lower layer and transfer top layer to
container after TA approves