- Are hydrocarbons that contain a carbon-carbon double bond.
- Are unsaturated—does not have the maximum number of hydrogen possible.
- Have suffix –ene
- Numbering of the carbon atoms begin at the end closest to the double bond.(double bond gets
the lowest number)
- Double bond does not need a number as numbering starts from the double bond.
- Numbering of double bond is required if there are more than 1 double bond.
- Rotation around double bond is prevented by high energy barrier; therefore some alkenes exist
in 2 forms. Cis-same side/Trans-opposite side.
- Are not possible for alkenes that have identical substituents attached to one of the carbons.
- They can interconvert only when the molecule absorbs sufficient heat or energy to cause the π
bond to break.
- Must have 2 different groups on the one carbon
- Must have the same atom/group on the opposite side of the double bond.
But cis/trans doesn’t work for all alkenes;
E/Z sequence alkenes
- For tri and tetra substituted alkenes - E =2 high priority groups on opposite sides
- Z=2 high priority groups on the same side
- Priority is assigned by looking at what is attached to the carbon at a time.
Step 1: Rank atoms by attached to the carbons in the double bond according to atomic number.
(When naming halogens use bromo, cloro, iodo, fluro)
Step 2: if the first atom is same, look at the second , third or fourth atoms away from the double
Step 3: multiple bonded atoms are equivalent to the same number of single bonded atoms.
-reactions occur because of the movement of valance electrons and a reaction mechanism tracks this
-electrons that initiate a reaction are accessible in π bonds or lone pairs.
-polar reactions: electrons move in pairs
-radical reactions: only one electron moves
-Based on polarity: interactions between electron rich and electron poor atoms.
-Electrophile: electron poor atom, electron loving and they accept a pair of electrons. (Usually
positively charged) (i.e. carbons/hydrogens)
-Nucleophile: electron rich atom, nucleus loving and they have a pair of electrons to share. (Usually
negatively charged) (i.e. halogens)
-reaction mechanisms: -a bond is formed when an electron rich atom donates a pair of electrons to an electron poor atom.
-electron movement is shown by a double headed arrow.
-curved arrows always start at the nucleophile and goes to electrophile.
-an arrow from a atom to a atom in a different molecule indicates new bond formed.
-and arrow from the middle of a bond to a atom in the same molecule indicates a bond broken.
-the highest energy structure involved in a reaction step, which cannot be isolated or directly observed
and it has partially formed bonds.
-a structure which can be sometimes isolated and has fully formed bonds.
-have higher energy th