Oils and Fats

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Slide 1

Oils and Fats

Slide 2

Chemical structure.

Oils and fats – important for storing chemical energy in living things.

Oils are liquids – fats are solids.

Made from esters of propane-1,2,3,triol (glycerol) + long chain carboxylic acids RCOOH.

Slide 3

Table 11 Common fatty acids

Slide 4

Types of triesters

Triesters (triglycerides) – 3 carboxylic acids react with triol.

Mixed triesters – three acid groups, not all alike often found in natural oils and fats.

Slide 5

Fats and fatty acids.

Unbranched hydrocarbon chains.

Called fatty acids – occur in fats!!!

Fully unsaturated / 3 or 4 double bonds.

Still known by old names – systematic names too long.

Thought to cause blockage of blood vessels and heart disease, especially the saturated ones.

Slide 6

Fat facts!

Natural oils and fats are mixtures of triesters.

Can be split up by hydrolysis, heat with conc. NaOH.

Triester + NaOH  glycerol + sodium salt of acid

Basis of soap manufacture eg. “Palmolive”

Convert sodium salts to free acids by adding dil. HCl or other mineral acid.

Slide 7

Solid or .?

Fatty acids present in mixture affect the properties.

Saturated triglycerides pack closely together.

Attractive forces - higher melting point.

Slide 8

…or Liquid?

Unsaturated triglyceride molecules cannot pack closely together because of cis double bonds - causes kinks!

Intermolecular forces are weaker.

Less energy needed to separate molecules - lower melting point.

Slide 9

Converting oil to fat.

Most natural oils need processing to make them fit for use.

Hydrogenation of unsaturated oils - make margarine.

Controlled hydrogenation makes oils more solid.

Pass H2 through heated oil - nickel catalyst.

Add flavourings, salt, vitamins etc.