Chapter 12 Flashcards
What is a sigma bond?
A sigma bond is the overlap of atomic orbitals directly between the bonding atoms
What is the effect of chain length on boiling point
As the chain length increases, molecules have a larger surface area
and more surface contact is possible between molecules.
->London forces are greater
->more energy required to overcome
Effect of branching on boiling point
As branching increases, there are fewer surface points of contact, leading to fewer London forces.
As branching increases, molecules cant get as close together as straight chains, leading to weaker London forces
->Less energy required to overcome them
What is the mechanism for halogenation of alkanes?
Radical Substitution
What is a Radical?
A very reactive species. An atom, or a group of atoms with unpaired electrons. Formed via homolytic fission
What is substitution?
An atom or a group of atoms has been replaced with another atom or group of atoms
What are the three stages of Radical Substitution?
Initiation
Propagation (Two parts)
Termination
What is homolytic fission?
Each atom takes one of the shared pair of electrons from the bond
Describe the first step of Radical substitution
Initiation: Formation of radicals via heterolytic fission (Energy provided by UV radiation)
Describe the second step of Radical substitution
Propagation : Radicals on both sides of the equations. A chain reaction.
(adding together the propagation steps gives the overall equation
Describe the third step of Radical substitution
Termination: Two radicals collide, forming a molecule with all electrons paired
Name some Limitations of radical substitution reactions
Further substitution
Substitution at different positions in carbon chain
->mixture of products
What is the shape and bond angle around each carbon ayom on alkanes
Tetrahedral, 109.5 because there are 4 bonding pairs and no lone pairs, which repel and move as far appart as possible
Shape and bond angle around the carbon atoms involved in a double bond
Triagonal planar, 120°
What is an electophile
An elecron pair acceptor
It is a positively charged ion or molecule with a slightly positive atom, which is attracted to a region of high electon density, where it accepts a pair of elecrons
Which products are the major and minor products?
The major product forms via the most stable carbocation intermediate.
A secondary carbocation is more stable than a primary carbocation
Give two uses for PVC
Floor tiles and imitation leather
Name 4 ways in which waste polymers can be reused
Recycling, PVC Recycling, using waste polymers as fuel, feedstock Recycling
