organic 1 p2 Flashcards
nomenclature
system used for naming organic compounds
empirical formula
simplest whole number ratio of atoms in a molecules
molecular formula
provides the actual number of atoms of different elements in a molecule
displayed formula
shows every atom and every bond in a molecule
structural formula
shows the arrangement of atoms in a molecule without showing every bond
skeletal formula
a type of formula which is drawn as line with each vertex being a carbon atom
carbon atoms not drawn, assumed each C atom has all unspecified bonds as C-H
homologous series
a series of organic compounds having the same functional group but with each successive member differing by CH2
functional group
a group of atoms responsible for characteristic reactions of a compound
suffixes for..
aldehyde
ketone
carboxylic acid
aldehyde = al
ketone = one
carboxylic acid = oic acid
alkane formula
CnH2n+2
alkene formula
CnH2n
saturated
organic compounds which only contain single bonds
unsaturated compounds
organic compounds that contain at least one carbon carbon double covalent bond
structural isomerism
when molecules have the same molecular formula but different structural formula
what are 3 ways in which structural isomers can be formed?
1 alkyl groups can be in different places
2 functional groups can be bonded to different parts
3 there can be different functional groups
stereoisomers
organic compounds with the same molecular formula but have different arrangement of atoms in space
what is E-Z isomerism and how are the E and Z isomers decided?
caused by limited rotation about the C=C double bonds
if the two substituents with the highest molecular mass are on the same side on the double bond (both above/both below) it is the Z isomer
what is cis-trans isomerism?
special type of E/Z isomerism where the two substituents of each carbon atom are the same
E - trans
Z - cis
homolytic fission
happens when each bonding atom receives one electron from the bonded pair forming two radicals
heterolytic fission
when one bonding atom receives both electrons from the bonded pair
what are radicals?
highly reactive, neutral species
how is a covalent bond formed from two radicals?
radicals collide and the electrons are involved in the bond formation
how are alkane fuels obtained?
fractional distillation, cracking and reforming crude oil
fractional distillation process
1 oil pre heated and passed into a column
2 fractions condense at different temps (temp is hottest at bottom)
3 separation of the fuels depends on boiling point which depends son size of molecules - the larger the molecule the larger the London forces
4 similar molecules condense together and so are collected at the same fraction
5 small molecules condense at the top at lower temps and big molecules condense at the bottom at higher temps
cracking
process of converting large hydrocarbons to smaller molecules by breakage of C-C bonds
reforming crude oil
processing of straight chain hydrocarbons into branched chain alkanes and cyclic hydrocarbons for efficient combustion
shape and angle of an alkane?
tetrahedral
109.5
describe the sigma bond in alkane
the sigma bond is a covalent bond which has a direct overlap of the electron clouds of the bonding atoms
how reactive are alkanes?
very unreactive
what reactions do alkanes undergo?
combustion and reaction with halogens
what type of reaction is combustion?
oxidation reaction
what is complete combustion?
combustion that occurs with plentiful supply of air
what are the products of complete combustion when alkanes are used?
carbon dioxide and water
what is the colour of the bunsen flame during complete combustion?
blue flame
what is incomplete combustion and what products are formed in the case of alkanes?
combustion in a limited supply of oxygen
products: water, carbon dioxide and carbon monoxide
what type of hydrocarbon are most likely to undergo incomplete combustion?
longer chains
what are the pollutants formed in the combustion of alkanes?
carbon monoxide, oxides of nitrogen and sulfur, carbon particulates and unburned hydrocarbons
what is the environmental impact of carbon monoxide?
it is toxic/poisonous
what is the environmental impact of soot (carbon)?
asthma, cancer, global dimming
what are the environmental impacts of nitrogen oxides?
NO is toxic and can form smog
NO2 is toxic and acidic and forms acid rain
what are the environmental impacts of unbranched hydrocarbons?
they contribute towards formation of smog
what is the importance of catalytic converters?
these remove CO, nitrogen and unburned hydrocarbons (e.g. octane) from exhaust gases turning them into less toxic products CO2, N2 and H2O
what are biofuels?
fuels developed from renewable resources
alcohols and biodiesel are two examples of renewable plant-based fuels
what are the advantages of biofuels?
+
- reduces use of non-renewable fuels
- use of biodiesel is more carbon-neutral
- fossil fuels can be used feedstock for organic compounds
- less large scale pollution
what are the disadvantages of biofuels?
- less food crops may be grown because crops for biofuel would be grown instead
- reduction of rainforests have to be cut down to provide land
- shortage of fertile soils
how are haloalkanes formed from alkanes
radical substitution
in the presence of what does alkane react with halogens?
UV light
what are the 3 stages of free radical substitution?
initiation - breaking halogen bond to form free radicals
Cl2 –> 2Cl .
propagation - chain part of the reaction where products are formed but free radical remains
Cl. + CH4 –> HCl + .CH3
.CH3 + Cl2 –> CH3Cl + Cl.
termination - free radicals removed, stable products formed
.CH3 + Cl. –> CH3Cl
2Cl. –> Cl2
.CH3 + .CH3 –> CH3CH3
what are the limitations of free radical substitution?
if there is excess halogen further substitution will take place therefore the desired product will be harder to separate from the others
how is a pi bond formed?
electrons in the adjacent p orbitals overlap above and below the carbon atoms
they can only be made after a sigma bond is formed
pi bonds restrict the rotation of carbon atoms
what is the angle and shape of a double bond?
trigonal planar 120*
what is the qualitative test for alkenes?
this tests for C=C double bond using bromine water
if the alkene is present bromine water decolourises
are alkenes(?) 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 alkenes have?
only London forces due to non-polar bonds
what are the types of isomers that can be formed using alkenes?
E/Z isomers - due to the restricted rotation
cis/trans isomers - if two of the same substituents are attached to each carbon
what is an electrophile?
species that are electron pair acceptors
what is the most stable type of carbocation intermediate? why?
alkyl groups have a positive inductive effect, so the most stable carbocation 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 available)
what conditions are needed for the electrophilic addition of H2O to an alkene? what is this type of reaction called?
steam in the presence of an acid catalyst, usually phosphoric acid (H3PO4)
reaction is called hydration
what is the product of the hydration reaction?
an alcohol
what conditions are needed for the electrophilic addition of a hydrogen halide to an alkene?
hydrogen halide gases must be at room temperature
what is the reaction called when a halogen is added to alkene?
halogenation
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 –> positive dipole atom attracted to double bond
how can an alkene be converted into alkane? what is the reaction called and what are the required conditions?
alkene + hydrogen = alkane
hydrogenation
conditions –> 150*C nickel catalyst
what is an addition polymer?
many monomers bonded together via rearrangement of bonds without the loss of any atom or molecule
what are monomers? what form do they usually take?
molecules which combine to form a polymer
usually have a C=C bond which breaks to leave a repeating pattern
what are the ways in which plastics can be disposed?
landfill, combustion, electricity generation, reuse, recycle, organic feedstock
what are the disadvantages of recyling?
plastics must be sorted into different types, expensive, labour intensive, requires high technology
how can chemists limit the problems caused by polymer disposal?
developing biodegradable polymers
removing toxic waste gases caused by incineration of plastics
explain what happens in organic feedstock
plastics are separated and broken down into small organic molecules through a series of reaction
the molecules can then be used produce plastics and in other industries
what are haloalkanes?
saturated organic compounds that contain carbon atoms and at least one halogen atoms
are haloalkanes soluble in water?
insoluble as C-H bonds are non-polar not compensated for enough C-X bond polarity
what type of intermolecular forces do haloalkanes have? why?
permanent dipole-dipole and London forces of attraction
C-X bond polarity creates permanent dipoles
do haloalkanes have a polar bond? why?
yes polar, as halogen has a higher electronegativity than C (halogen is delta -, carbon is delta +)
when would haloalkanes have higher boiling points?
increase Carbon chain length
halogen further down group 7 (e.g. I)
how would the mass of a haloalkane compare with the mass of an alkane of the same chain length?
greater as mass of halogen > mass of H
what is the most important factor in determining halogen reactivity?
the strength of carbon halogen bond
what would bond polarity suggest the order of reactivity haloalkanes be?
C-F would be most reactive as most polar bond
what would bond enthalpies suggest the order of reactivity of haloalkanes be?
C-I would be most reactive as lowest bond enthalpy
what is the trend in reactivity of primary, secondary and tertiary haloalkanes?
tertiary halide produces a ppt almost instantly
secondary halide gives a slight ppt after a few seconds
primary halide takes considerably longer to produce a precipitate
nucleophile
electron pair donor
e.g. OH-, CN-, NH3
what is nucleophilic substitution?
a reaction where a nucleophile donates a lone pair of electrons to delta + C atom, delta - atom leaves molecule (replaced by nucleophiles)
hydrolysis
a reaction where water is a reactant
what reactant often produces hydroxide ions for hydrolysis?
water
what fission does water undergo to produce OH-?
heterolytic fission
what are the conditions/reactants needed for elimination reaction of haloalkanes?
NaOH or KOH dissolved in ethanol (no water present)
heated
what is formed in elimination reaction of haloalkanes?
an alkene, water and halogen ion
how can you convert a haloalkane into an amine?
reagent: NH3 dissolved in ethanol
conditions: heating under pressure in a sealed tube
mechanism: nucleophilic substitution
type of reagent: nucleophile - ammonia
how do you convert haloalkane into alkene?
use ethanolic potassium hydroxide to produce alkenes (where the hydroxide ion acts as a base)
how do you produce nitriles from haloalkane?
use potassium cyanide to produce nitriles (where the cyanide ion acts as a nucleophile)
how can you compare the rate of hydrolysis of haloakanes?
aqueous silver nitrate is added to a haloalkane and a silver halide precipitation is formed
the quicker the precipitate is formed the faster the rate of hydrolysis
AgI(s) - yellow precipitate
AgBr(s) - cream ppt
AgCl(s) - white ppt
AgCl forms the slowest
what is the functional group of an alcohol?
hydroxyl group -OH
general formula of an alcohol
CnH2n+1OH
alcohol prefix/suffix?
Hydroxyl-
-ol
what kind of intermolecular forces do alcohols have? why?
hydrogen bonding, due to the electronegativity difference in the OH bond
how do alcohols’ melting point and boiling point compare to other hydrocarbons’ of similar C chain lengths? why?
higher, because they have hydrogen bonding (strongest type of intermolecular force) –> stronger than London forces
are alcohols soluble in water? why does solubility depend on chain length?
soluble when short chain - OH hydrogen bonds to hydrogen bond in water
insoluble when long chain - non polarity of C-H bond takes precedence
what makes an alcohol primary?
C bonded to OH is bonded to one other C atom
what makes an alcohol secondary?
C bonded to OH is bonded to two other C atoms
what makes an alcohol tertiary?
C bonded to OH to three other C atoms
what forms if you partially oxidise a primary alcohol?
an aldehyde
what conditions are needed to partially oxidise a primary alcohol?
dilute sulfuric acid, potassium dichromate (VI). distil product as it’s produced, gentle heating
write an equation for the partial oxidation of ethanol
CH3CH2OH(l) + [O] –> CH3CHO(g) + H2O(l)
what forms if you fully oxidise a primary alcohol?
a carboxylic acid
what conditions are needed to fully oxidise a primary alcohol?
concentrated sulfuric acid, potassium dichromate (VI), reflux, strong heating
equation for the full oxidation of ethanol
CH3CH2OH(l) + 2[O] –> CH3COOH(g) +H2O
what forms is you oxidise a secondary alcohol?
a ketone
what conditions are needed for the oxidation of a secondary alcohol?
concentrated sulfuric acid, potassium dichromate (VI), strong heating
is it possible to oxidise tertiary alcohol?
no
what is a dehydration reaction?
a reaction where water is lost to form an organic compound
what are the products of dehydration reaction of alcohol and the conditions needed?
alkene and water
conc sulfuric acid or conc phosphoric acid and 170*C
how can you produce chloroalkanes from alcohols?
use PCl5 (PCl3/ conc HCl/ SOCl2 / mixture of NaCl + H2SO4 can all also be used for substituting a Cl)
e.g. CH3CH2OH + PCl5 –> CH3CH2Cl + POCl3 + HCl
how can you produce bromoalkanes from alcohols?
use 50% conc sulfuric acid and potassium bromide
how can you produce iodoalkanes from alcohols?
use red phosphorus and iodine
PI3 + 3CH3CH2OH –> 3CH2CH2I + H2PO3
how do you prepare and purify of a liquid organic compound?
1 heat under reflux
2 extract with a solvent in a separating funnel
3 distil
4 dry with an anhydrous salt
5 determine boiling temperature
