Organic 2 - Chapter 13 & 14 Flashcards
What is a haloalkane
It is an alkane with hydrogen atoms substituted by halogen atoms
What are the classifications of haloalkanes
Primary
Secondary
Tertiary
What is primary
Halogen at the end of the carbon chainn
What is secondary
Halogen in the middle of carbon chain
What is tertiary
Halogen at junction of 2 carbon chains
What are nucleophiles
Electron pair donors
What reactions do haloalkanes do
Nucleophilic substitution where the halogen is replaced by an electron pair donor
Elimination reactions
What affects the rate of reaction for haloalkanes
The strength of the carbon halogen bonds
The reaction gets quicker down group 7
What are common nucleophiles
Hydroxide ion OH-
Cyanide ion CN-
Ammonia NH3-
What is a nucleophilic substitution
It is where an electron pair donor replaces another atom or group of atoms during a reaction
What is the general mechanism of nucleophilic substitution
The nucleophile attacks the carbon attached to the halogen
The bond breaks between the carbon and halogen towards the halogen
The nucleophile replaces the halogen
What is different about the mechanism with ammonia
It requires 2 ammonia’s
It takes 2 stages forming NH2 at the point
What are elimination reaction
It is one in which an atom or group of atoms is removed from a reactant
What are the conditions for elimination
The reactant must be dissolved in ethanol not water and must be heated
What are the products of elimination reactions
Alkene
Halogen with group 1 atom
Water
What is the general mechanism for elimination reactions
The hydroxide ion attacks a hydrogen
The bond between the carbon and hydrogen breaks and goes to a carbon carbon bond
This breaks the halogen carbon bond
Forms an alkene
What conditions are there for nucleophilic substitution
Aqueous hydroxide ions and warm
What structures favour elimination or substitution
Primary - Substitution
Secondary - Both
Tertiary - Elimination
What happens if the haloalkane is unsymmetrical when eliminated
Multiple isomeric products
What are alkenes
They are unsaturated hydrocarbons with the general formula Cn H2n
What happens to boiling point as Mr rises
It rises
What does E and Z stand for
E - opposite
Z - together
How do you use CIP to assign E/Z
Look at the atomic number of the atoms attached directly to the double carbon bond ( or subsequent atoms if they are the same)
Highest values opposite = E
Highest value together = Z
Are alkenes soluble
They are virtually insoluble in water
What reactions do alkenes carry out
Combustion
Electrophilic additions
How do alkenes combust
They burn to form Carbon dioxide and water
They are not used as fuels though
Why aren’t alkenes used as fuels
Because they are more valuable for other purposes
What is electrophilic addition
Where the double bond will accept atoms to form an alkane from an alkene
How does the addition of hydrogen happen
It happens in the presense of the finely divided Ni catalyst at about 150 degrees
Used to make margarine
How does the addition of halogens work
What is the mechanism
Alkenes react quickly with halogens to produce haloalkanes
Double carbon bond attacks electropositive halogen
This breaks the halogen bond towards the other halogen
This forms a carbocation
The other halogen ion reacts with the carbocation
How does the addition of hydrogen halides work
What is the mechanism
Hydrogen halides react with alkenes to form haloalkanes
Hydrogen is attacked by double carbon bond
This breaks the hydrogen halide bond towards the halogen
This forms a carbocation
The halide ion attacks the carbocation
How does the addition of sulphuric acid work
What is the mechanism
Forms and alkyl hydrogensulphate
Double bond attacks hydrogen
Bond breaks between oxygen and hydrogen towards oxygen
Forms a carbocation
OSO3H - attacks carbocation
What are alkyl hydrogen sulphates used for
They are converted into alcohols by reaction with water (hydrolysis)
What happens when unsymmetrical molecules react with unsymmetrical alkenes in an addition reaction
You can get more than 1 product
What is the trend in stability across the types of carbocation intermediates
Primary is the least stable
Tertiary is the most stable
Alkyl groups push electrons towards C+ so more stable
The product formed will be from the most stable carbocation
What is polymerisation
A process in which lots of small molecules called monomers join together to form a large molecule (polymer) which consists of repeating units
What types of polymers are there
Naturally occuring or synthetic
Addition or condensation polymers
What are addition polymers
They are long chain molecules formed when lots of small molecules join together to form a polymer with nothing else formed
What affects the properties of polymers
Chemical structure and intermolecular forces
What are plasticisers
They are molecules that push chains apart which means the IMF are weaker and so are more flexible
What is the problem with addition polymers
They are unreactive and so non-biodegradable
What are alcohols
A homologous series of compounds with general formula Cn H2n+1 OH
What is the trend in BP of alcohols
Increases as mr increases
Are alcohols soluble in water
The short chain alcohols are soluble due to hydrogen bonding
What ways can alcohols be made
Hydration of ethene - Alkenes react with steam
Fermentation of sugars
How does the hydration of ethene work
Double carbon bond attacks hydrogen ion (from acid)
This forms a carbocation
Oxygen from water attacks carbocation
Hydrogen bonded onto oxygen breaks bond
What conditions are required for fermentation and Hydration of ethene
35 degrees
anaerobic
300 degrees
high pressure
What is dehydration
It is the removal of water
What alcohols can be dehydrated
That have a hydrogen atom on the Carbon next to the carbon with the OH group
What does the dehydration of alcohols produce
alkene
Water
hydrogen ion
What mechanism is used to dehydrate alcohol and how
elimination
The lone pair on the oxygen attacks the H+ ion (from the acid) and bonds
The hydrogen next to the OH breaks off towards C-C bond
The positively charged oxygen breaks off from carbon towards oxygen
What conditions are used for the dehydration of alcohols
sulfuric acid or phosphoric acid
180 degrees
What is dehydration used for
Produces alkene from a renewable source
Makes polymers
What is electronegativity
The (relative) tendency of an atom to attract a pair of electrons/ the electrons/ electron density in a covalent bond
