organic chemistry Flashcards
carbon
carbon atoms have strong covalent bonds to eachother
the carbon carbon bonds can be single,double or triple
how can carbon atoms be arranged as
straight chains
branched chains
rings
functional group
group of atoms or an atom that give specific properties to a molecule
homologous series
group of atoms with the same functional group
organic compound is determined by
functional group
alkanes
c2H2N+2
c-c
Alkenes
cnh2n
c=c
brackets in structural formula show its a
branch
nomenclature
Structural isomerism
Same molecular formula but different structural formula
Chain isomerism
Position isomerism
Chain isomerism
Different arrangement of the carbin skeleton
Similar chemical properties
Slightly different physical properties
More branching so lower boiling point
Positional isomerism
Same carbon skeleton
Same functional group
Functional group is in a different position
Similar chemical properties slightl different physical properties
Functional group
Different functional
Different chemical properties
Different physical properties
Hexane
Straight chains can pack together
Increased intermolecular forces
Higher boiling point
alkanes
saturated hydrocarbons
single carbon- carbo bonds and single carbon-hydrogen bonds only
-CnH2n+2
every bond is a pair of electrons is they repel each other
molecular formula
it shows the number of each type of atom
structural formula
it shows the positions of the atoms
displayed formula
displays all the bonds
alkanes isomerism
the only type of isomerism that alkanes can posses is chain isomerism this is a type pf structural isomerism
properties of alkanes
alkanes do not dissolve in. water this is because they are non polar the electronegativity of carbon and hydrogen is similar
because the water molecules are held together by hydrogen bonds and alkanes by van Der wall forces they do not interact with each other
straight chains can pack together nicely and have increased intermolecular forces high bp than branched chains
boiling points of alkanes
increasing intermolecular forces causes boiling points to increase as the chain length increases
shorter chains are gases at rtp
pentane is a liquid and 18 carbon chain is a solid
solubility of alkanes
insoluble in water as waters hydrogen bonds are stronger than van Der Waals between alkanes. they mix with non polar liquid
fraction; distillation
used to separate different molecules of crude oil for different uses
oil refining
involves the separation of these hydrocarbons into mixtures which new very important and extremely Z
1)crude oil is vaporise and passed into colomn
2)the temperature of column decrease upwards
3)fractions condense at different heights
vacuum distillation unit
1)heavy residues from the fractionating column are distilled again under vacuum
2)lowering the pressure over a liquid will lower its boiling point
3)vacuum distillation allows heavier fractions to be further separated without high temp which could break them down
cracking
conversion of large hydrocarbons to smaller hydrocarbon molecules by breakage of c-c
high Mr alkanes converted into smaller mr alkanes + alkanes + hydrogen
this is a chemical process involving the splitting of strong covalent bonds so requires high temperature
two main types of cracking
thermal and catalytic
thermal cracking conditions
7000kpa
400-900 degree c
produces mostly alkenes
sometimes produces hydrogen
catalytic cracking conditions
low pressure
450 degrees
zeolite catalyst
produces branched and cyclic alkanes and aromatic hydrocarbons
used for making motor fuels
branched and cycle hydrocarbons burn more cleanly and are used to give fuels of a higher octane number
economic reasons for cracking
-petroleum fractions with shorter carbon chains are now in more demand than larger
-make use of excess longer hydrocarbons
-supply demand for shorter ones
-products of cracking are more valuable than the startijg materials
zeolite catalysts
honey Combe structure to give enormous surface area wthey consist of silicon dioxide and aluminium oxide 1
equation for the complete combustion of methane
ch4+2o2-> co2+ 20-2h2o
are alkanes reactive
very unreactive
wont react with acids, bases,oxidising agents
flammable
react with halogens in the right conditions
mmore carbons present
more energy released
more bonds being broken
what is propane used for
camping gas
probkems of burning fossil fuels
-carbon monoxide - toxic and odourless
-carbon itnto partiuclates due to incomplete combustion and causeds respiritory problems
-unburnt hydrocarbons
where does sulfur come from
from muscle in beings even after death sulfer emains as atoms so when burnt react wth oxygen and creates sulfer dioxude
why is it importn t for ur car to be swervcied regularly
soot is created envionmental damage
why do cars produce more poluution when first started up
engine - cold poor mixing of fuel vapour in oxygen ,need to geat up the engine
why is liquid dripping from a car exhaust pipe a bad sign
unburnt hydrocarbons
why carbon monoxide is toxiuc
asthma
carcinogens
competed with oxygen to bind to haemoglobin
catalytic converter
remove co2 and NOx and unburned hydrocarbons from the exhaust gases turning them into harmless co2 n2 and h2o
how converterss sadapted
ceramic honeycomb coated with a thin layer of catysyted metals to give a large surface area
free radical substitution
x÷y - .=unpaired electron
1) x+. electron defificnt -electrophiles
:y- takes electrons -nucleophiles
heterocatalytic fission ions are formed
2)x+ + :y-
eg. h:CL-> h+. +cl-.
the unpaired electrons in free radicals are available for bonding
free radicals properties
reactive species which posses an unpaired electeon
-their reactivity is due to them wanting to pair up the single electron
-formed by homiletic fission of covalent bond
-formed during the reaction between the chlorine and methane
-formed during thermal cracking
-involved in the reaction taking place in the ozone layer
Haloalkanes
when one of more of the hydrogen atoms replaced by a halogen
contain more than one type of halogen for example CFCs contain both fluorine and fluorine atoms
prefixes
Fluoro for fluorine
Chloro for chlroine
Bromo for bromine
Iodo for iodine
-alphabetical order
name of the halogenoalkane is based on
he orignal alkane
So CH3CH2CH2Br would be 1-bromopropane
The position of the halogen atom must be taken into account
So CH3CH(Br)CH3 would be 2-bromopropane
Finally the substituents are listed alphabetically
So CH3CH(Cl)CH2Br would be 1-bromo-2-chloropropane
Halogenoalkanes can be classified as
primary, secondary or tertiary depending on the number of carbon atoms attached to the C-X functional group
primary halogenoalkane
1
have one R group attached to the carbon linked to the halogen
when a halogen is attached to a carbon that itself is attached to one other alkyl group
secondary halogenoalkane
when a halogen is attached to a carbon that itself is attached to two other alkyl groups
bond polarity of haolegnokalnes
-halogens are more electronegative than carbon so the carbon bonded to the halogen has a partial positive charge it is electron deficient
attached by reagents that are electron ring -nucleophiles
more polar bond more reactive it is
what is a nucleophile
a species that has a lone pair of electrons which it can form a bond by donating its electrons with which it can form a bond by donating its electrons to an electron deficient carbon atoms
three nueclophile ions
oh-
cycanide - cn-
ammonium ion
reactions with nucleophiles
nucelphilic substitution
1)nucleophile uses its lone pair to provide the electrons for a new bond
2)the halogen is displaced carbon can only have 8 electrons in its outer shell
3)the result is subsitiution following attack by neociophil
4)the mechanism is therefore known as nucelophillic subsitiution
easiest halogen to break off
iodine
weakest to strongest bond
c-l
c-br
c-cl
conditions of nucelophillic subsitiuton
1)aqueous solution or pot/sod hydroxde
2)reflux in aqueous sol
3)alcohol
4)hydroxide ion OH-
isomeric alkenes being formed
what is a base
a molecule that has the ability to accept a potion acceptor
the oh ion removes the h+ ions from the haloalkane
this gives us an elimination reaction rather than a substitution reaction
condition for making isomeric alkenes
the potassium or sodium hydroxide is dissolved in ethanol and mixed with the haloalkane
there is no water present and mixture is heated
mechanic, of elimination
1)the oh ion uses its lone pair to form a bond with one of the hydrogen atoms not eh carbon next to the c-br bond
Synthetic halo alkanes
The reactivity of the C-X BOND means that haloalkanes play an important part in sythentic organic chemistry
The halogen can. E replaced by a variety of groups via nucleophillic substitution
Use of haloalkanes
Crewsts useful polymers from halogens hydrocarbon
Monomer of haloalkane
Chloroethen
Polymer of haloalkane
Poly chloroethene
PVC
Properties of Alkenes
Hydrocarbons -contain only h and c atoms
Have at least one double bonds between two of their carbons
Unsaturated -
Cnh2n
What’s special about a double carbon bond
Each carbin have 4 outer shell electrons which it can use to form binds
When carbon forms single bonds it uses sigma bind
When carbon forms double bonds it uses ome sigma bond and one pi bond
Pi bond forms by the sideways overlap of 2 p orbitals
Cip rules properties
Priority based on atomic number
All c=c compounds
What reactions do Alkenes undergo
-burn in air or oxygen -unimportant too valuable to waste in this way
-important reactions occur around double carbon bond -addition reaction pi bond breaks so electrons used to join the 2 carbon atoms to other things
Electrophile
An electron pair acceptor
Accepts a lone pair of electrons
Attracted to areas of high electron density
Alkenes and hydrogen halides w
Halogenoalkanes
Reaction with Alkenes and halogens
Makes dihalogenoalkanes
Alkenes and concentrated sulfuric acid
Makes alkyl hydorgensulfates and in turn alcohols
Alkenes and water
Makes alcohol
stability trend in alkenes
-electron donating ability of alkyl groups
-each alkyl group pushed electrons towards c+ charge of carbocations
-a positive charge is spread over alkyl group
-the more the [positive charge is spread out
-the greater the stability of the carbocation
Addition polymers
Made from alkene monomers
Pi binds breaks open in each monomer to join together
Produce long saturated chains containing no double bonds
Many different polymers produced from different monomers
Plasticiser
Flexible
Lower boiling point
Lower melting point
Ldpe
High pressure
High temperature
Via free radical mwxnjnsm
Highly branched molecule due to random nature of free radical reactions
Hdpe
Pressure an temperature
Ziegler - natta catalyst
Very little branching one branch per every 200 carbon atoms
Ldpe key characteristics
Can’t handle low temperature
Good resistance
Good resistance to chemicals
Low compatibility with addictive
Highly flammability
Hdpe characteristics
Flexible
Weatherproof
Can handle low temps
Low cost
Good chem resistance
Two forms of tackling plastic pollution
Mechanical
Feedstock
Mechanical
Sperates plastics by type
Washed and ground into pellets
Can be melted and remoulded
Feedstock
Heated until polymer bonds are broken -monomers are reformed
Monomers are then used to make new plastics
Aliphatic
Aromatic
Oh replaces an h in a basic hydrocarbon skeleton
Cnh2h+1oh
Aromatic
Oh is attached directly to the ring
An oh on a side chain of a ring behaves as a typical aliphatic alcohol
Oh group attached directly to the ring
Structural differences between aliphatic and aromatic
-alcohols are classified according to the environment of the oh group
-chemical behaviour eg.oxidation ,often depend on structural type
Advantage of of fermentation
-low energy process
-simple equipment
-uses renewable resources
Cons of fermentation
-slow -batch processes
-produces impure ethanol
Advantages of hydration of ethene
Fast
Pure ethanol produced
Continuous process
Cons of hydration
High energy
Expensive plant required
Uses non renewable fossil fuels
Oxidation of alcohols
Uses acidified potassium dichromate
Primary alcohols
Oxidised to an aldehyde and cooh
Secondary alcohol
Oxidised to a ketone
Tertiary alcohol
Can’t oxidesed using oxidising agent
Mass spectrum
Spectra obtained for organic molecules have many peaks
Each peak is due to a particular fragment with a certain
how optical isomers formed
carbonyl compounds undego nucleophillic subsitiuion
if there are two different groups attached to the c=o bond ,
the posssibility of foming optical isomers arises
carbonyl compounds - nucleophillic addition
reagent - potassium cyanide and dilute acid
reflux
cn- ion
hydroxyl nitrile
hcn is a weak acid and has diffuiuvlty disaassociating
using ionic kcn produces more of the nucleophile cn-
reaction with naBH4
sodium tetrahydridoborate
aqueous or alcholic solution
nucleophillic addition
h-
alc reduced to primary
ketones reduced to secondary alcs
water provides a proton
why doesnt nabh4 reduce c=c bonds
-h
c=c negative
it is repelled by high electron density ofv the double carboon bond
carbonyl compounds - reduction with hydrogen
hydrogen
nockel catalyst
hydrogenation - reduction w electrophillic addition
alcohols aldehydes are redyced to primary alcs
ketones reduced to secondary alcs
two cabroxyl groups
dioic
boiling point for carboxylics
increases as size increases
higher induce dipoole dipole interactions
higher for straight chains isomers
solubility
carboxylic acidd are soluble in organic solevents
they are also soluble in water due to hyrodgen bonding
small ones dissolve readily in cold water
as mass increases the solubility decreases
benzoic acid is fairly insoluble in cold but soluble in hot water
esterification
alcohol + strong acid catalyst
reflux
ester
preperation of esters
alcohol + acyl chloride
reflux under dry conditions
acyl chlorides are very reactive but must be kept dry as they react with water
preperation of esters
alcohol + acid anyhrdie
refluc under dry condition]acid anhydrides are not as reactive as acyl chlorides so the reaction is slower
the reaction is safer and less exo thermic
acid anhydrides are less toxic
use of esters
fruitier and sweeter semll than aldehydes and ketones and are responsible for many natural flower smells
testing fir alcohols
the sweet and fruit smel of an ester can be used as a test to prove its an ester
the unkown substance can be warmed with carboxylic aicd in the presence of conc sulfuric acid
it will make a sweer smeell if it was orignally an oh
if no sweer smell exces acid with its pungest vinegary smell can be removed by ading warm aq sodium carbonate sol effercesence of co2
if remaining mixture has a sweet smell of an ester this co forms that it was orignally an alcohol
Smaller esters
More soluble due to their attraction to water
Less hydrophobic less repelling
Hydrolysis of esters
Ester +water = Carboxylic acid + alcohol
Hydrolysis of esters
If the hydrolysis takes place under alkaline conditions the organic product is a water soluble ionic salt
The Carboxylic acid can be made by treating the salt with hcl
Acyl chloride reactions
Reactive organic compounds that undergo many reaction such as nucleophile addition -elimination reaction
In a nucleophillic addition elimination of a small molecule across the c=o bond followed by elimination of a small molecule
Eg. Of NAE -hydrolysis ,alcohol reactions
Hydrolysis
Of acyl chlorides result in the formation of a Carboxylic acid and hcl molecule
This is a nucleophillic addition elimination reaction
A water molecule adds across the c=o bond
A hcl molecules is eliminated
Formation of amide
Acyl chlorides can form amides worn primary amines and ammonia
The nitrogen atom in ammonia amd primary amine has a lone pair of electrons which can be used to attack the carbonyl carbon atom in the acyl chlorides
The product in an amide when reacted with ammonia
Nucleophilles in nucleophillic addition elimination
1)ammonia
2)primary amines
3)alcohol
4)water
