3.4 Alkenes Flashcards
What is an alkene?
Unsaturated hydrocarbons with a C=C double bond
What is the general formula of an alkene?
CnH2n
Why is there no rotation about the C=C double bond?
Due to the π (pi) orbital - electron density above and below the single bond, which holds the carbon atoms in place
Are they more or less reactive than alkanes? Why?
More reactive, due to high electron density of double bond and the fact the pi-bond is slightly easier to break
What intermolecular forces of attraction do they have?
What intermolecular forces of attraction do they have?
Are they soluble in water? Why?
No, non-polar bonds (van der Waals’ < hydrogen bonding)
Name and describe the three kinds of isomers alkenes can have
Chain isomers (branched chains) Position isomers (C=C on different carbon atom) Geometric E-Z isomers (Z is when 2 highest atomic number chains are on the same side of the double bond; E is when they're on opposite sides)
What is an electrophile?
Electron deficient atoms/ions which accept a pair of electrons (here, from the C=C double bond
What is the most stable kind of carbocation intermediate? Why?
Alkyl groups have a positive inductive effect, so the most stable carbonation is the one bonded to the most other carbon atoms i.e. A tertiary carbocation
Major products will be formed from which kinds of
carbocations?
Tertiary (or the most stable avaliable)
What conditions are needed for the electrophilic addition of H2O to an alkene?
Acid catalyst, usually phosphoric acid
What are the product(s) of the reaction?
An alcohol
What conditions are needed for the electrophilic
addition of a hydrogen halide to an alkene?
Room temperature
What conditions are needed for the electrophilic
addition of a halogen molecule to an alkene?
Room temperature and organic solvent
How does a molecule with a non-polar bond react as if it is an electrophile?
C=C double bond with a high electron density induces a temporary dipole in the halogen molecule → δ+ atom attracted to double bond
