general shit Flashcards
What type of addition can alkenes undergo
electrophilic addition
what is an electrophile
electrophiles are electron pair acceptors which are attracted to areas of high electron density
why are electrophiles attractred to carbon double bonds
the carbon double bonds have high electron density
what happens to the carbon double bonds ion electrophilic addition
the double bond opens up and atoms get added to the carbon atoms
what reaction with alkenes produces an alkane
hydrogenation
what are conditions for hydrogenation
alkenes will react with hydrogen and a nickel catalyst at 150 degrees
what forms when halogens react with alkenes
dihaloalkanes
what reaction with alkenes produces alcohols
steam hydration
conditions for steam hydration
hydrated by steam at 300 degrees
pressure of 60-70 atm
phosphoric acid catalyst
reversible reactions cause low yeld unlessyou recycle
why are alcohols polar
the hydroxyl group is electronegative which pulls electron density away from the carbon atom
why are alcohols siluble in water
the partially positive hydrogen in the OH bond can form hydrogen bonds with oxygens from neighbouring molecules. hydrogen bonds are formed between the oxygens in water which lets alcohols mix freely
what happens to the solubility of alcohols as they increase in size
solubility decreases as most of the molecule is non-polar. causing less attraction for the for the H2O molecules
what reactions do alcohols have to form haloalkanes
alcohols can react with compounds containing halide ions in a substitution reaction causing the OH group to be replaces with a halogen forming a haloalkane
how do alcohols become alkenes
alcohols become alkenes through dehydration reactions
what is a dehydration reaction
eliminating water from alcohols in an elimination reaction
how does a dehydration reaction happen
the alcohol is mixed with an acid catalyst (sulfuric or phosphoric, both concentrated) then heated
where does the water come from in dehydration reactions
the water molecule is made up from the hydrixyl group and a hydrogen atom that was bonded to a carbon atom adjacent to the hydroxyl carbon
what does burning alcohol in a plentiful supply of oxygen cause
its causes combustion of the alcohol
what are products of combustion
CO2 and H2O
what are primary alcohols oxidied to?
primary alcohols are oxidised to aldehydes adn then to carboxylic acids
what are secondary alcohols oxidised to?
secondary alcohols are oxidised to ketones only
what are tertiaty alcohols oxidised to
they dont oxidise
how are aldehydes formed from primary alcohols
aldehydes are formed by gently heating excess alcohol with a controlled amount of oxidising agent in a distilling apparatus
how are carboxylic acids formed from primary alcohols
the alcohol is mixed with excess oxidising agent and heated under reflux
how are ketones formed from secondary alcohols
reflux the alcohol with acidified potassium dichromate
what is the only way to oxidise a tertiary alcohol
burn the fucker
what are stereoisomers
stereoisomers have the same structureal formula but are arranged differently in space
what causes stereoisomers
restricted rotation in the double carbon bond
what are z-isomers
a z isomer is when it has the same groups above or below the double bond
what is an E isomer
and E isomer is when the same groups are positioned accross the double bond
what is a sigma bond
a sigma bond is formed when two S orbitals overlap each other
the two s orbitals overlap in a striaght line, this gives the highest possible electron density between the two nuclei. this is a single covalent bond
what is a pi bond
a pi bond is formed by the sideways overlap of two adjacent p orbitals
it has 2 parts to it, one above and one below the the moloecular axis due to the dumbell shape of the p oribtal,
why are pi bonds weaker
pi bonds are weaker than sigma bonds because the electron density is spread out above and below the nuclei. this means that the electrostatic attraction between the nuclei and the shared pair of electrons is weaker, therfore pi bonds have a relatively low bond enthalpy
why are alkenes reactive
this is because of the double bond. the double bond contains high electron density (2 lone pairs) causing electrophiles to be attractred to it. it also contains pi bonds which have their electrons above and below the rest of the molecule making it likely to be attacked by electrophiles
def of a covalent bond
a covalent bond is the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
def of average bond enthalpy
the enrgy required to break a covalent bond
what is a dative covalent bond
this is where both electrons come from one atom
relative isotopic mass definition
mass compared with 1/12th mass of carbon-12
relative atomic mass def
weighted mean mass
compared with 1/12th mass of carbon-12
empirical formula
simplest whole number ratio of atoms in a molecule
products of incomplete combustion
carbon dioxide
water
pure carbon
carbon monoxide
hydrocarbons
