Announcements & Agenda (03/05/07). Pick up Movie Quiz Exam next Wednesday! Covers Ch 7, 8, 10-12 Will post a practice exam by Wed Grade sheets will be given on Wed (sorry ) Come visit Bob!!! Today Cis-trans isomers (11.2) Reactivity of unsaturated compounds (11.3)
These are some of the most important biological functional groups!
Know “ene” means alkene group present
Know “yne” means alkyne group present
linoleic acid, a fatty acid
an alkene group
a carboxylic acid group
According to VSEPR theory:
between atoms, and is called a “sigma” (σ) bond.
(not directly between the atoms) and is called a
“pi” (π) bond.
bond part of a double bond can’t rotate – you’d
have to break it.
In an alkene, the double bond
CH3 CH3 CH3
CH = CH CH = CH
(similar groups on same side) (similar groups on opp. sides)
(not cis or trans) (not cis or trans)
Present in Rhodopsin
From Lehninger Principles of Biochemistry 3rd ed.
Adding H2 to double
bonds in vegetable
In vegetable oils, the unsaturated fats usually contain cis double bonds.
CH3─CH=CH─CH3 + H─OH CH3─CH─CH─CH3
When hydration occurs with a double bond that has an
unequal number of H atoms,
CH3─CH=CH2 + H─OHCH3─CH─CH2
Write the addition product for each of the following:
1. CH3─CH2─CH=CH─CH2─CH3 + HOH
2. CH3─C=CH─CH2─CH3 + HOH
3. CH3─CH=CH─CH3 + H2
4. + HOH
2. CH3─C─CH─CH2─CH3 3. CH3─CH2-CH2─CH3
One Last Thing about Hydration…Hydration is also reversible – the equilibrium amounts of alkene compared to alcohol depend on how much water is around.
Lots of water – the reaction tends to use up as much water as it can, and most of the alkene forms alcohol.
If water is removed, water can be pulled off from alcohol to form the alkene. (concentrated acid).
Spring Breakers: Why too much UV is bad… A Reaction of Double Bonds!
DNA damage by UV radiation: induces dimerization of DNA bases (particularly T-T)
0 Double Bonds!Conjugated bonds
One Important Example: Benzene (Know This One!)
Aromatics are compounds that have conjugated pi bonds around a ring. Electrons love this, and aromatics are very stable.
Aromatics can be bad too Many are carcinogens! Can interact with DNA.
0 Double Bonds!Aromatic rings can include N atoms, too.