Mod 4 Flashcards
What is a hydrocarbon
. Compound consist of carbon and hydrogen atoms only
What is a saturated compound
. Has only single bonds
. What is an unsaturated compound
. Contains at least one carbon to carbon multiple bond
What is an aliphatic compound
. Where the carbon atoms are joined together to form a straight chain branched or unbranched
What is an alicyclic compound
. Where the carbon atoms are joined together in a ring structure
What is an aromatic compound
. Compound containing a benzene ring
What is a homologous series
. Series of organic compounds with the same functional groups but with each successive member different by CH2
What is a functional group
. Part of the organic molecule or a group of atoms responsible for its chemical reactions
What is an alkane
. Homologous series with the general formula CNH2N +2
What is a general formula
. Simplest algebraic formula of a member of a homologous series
What are the three types of structural isomerism
. Chain isomerism - hydrocarbons can be branched or unbranched
. Positional isomerism - functional group can be a different position
. Functional group isomerism - functional group can be different all together
Aldehyde, ketone, ester, amine
. O=C-H, al e.g. propanal
. O=C, one e.g. propanone
. C-O-C, oate, e.g. methyl propanoate
. C-N-Hx2, amine, propylamine
What are the properties of alkanes
. Nonpolar molecules as there is no significant difference between electronegativity of carbon and hydrogen
. Based on carbon carbon covalent bonds
. Very unreactive to a broad range of chemicals
. Are used extensively as fuels
What is the structure and bonding around c atom in alkanes
. There are 4 bonding present 0 lone pairs are in each carbon atom
. All electron pairs repel
. molecule forms a tetrahedral shape around each carbon atom
. Bond angles around each carbon will be 109.5°
What is a sigma bond
. And on end overlap of bonding orbitals directly between atoms (in all single bonds)
What is bond rotation in an alkane
. All bonds in an alkane can rotate
Boiling in melting points relating to hydrocarbons
. Longer chain equals higher melting and boiling points due to more points of surface contact between molecules so strength of induced dipole dipole interaction increases between molecules which requires more energy to overcome
. branched isomers have lower boiling points due to less points of surface contact so weaker induced dipole dipole interaction between molecules that require less energy to overcome
What is combustion and Write equation for the combustion of alkanes
. Complete combustion-burning of a substance in excess supply of oxygen
. I.e CH4 + 2O2 —> CO2 + 2H2O
. Incomplete combustion-burning of a substance in limited supply of oxygen
. I.e. CH4 + 1.5O2 —> CO + 2H2O
. I.e. CH4 + O2 —> C + 2H2O
What kind of hydrocarbons are more efficient as fuels
. Branched chains are preferred to be used as fuels as they have more efficient combustion
What is a radical
. A highly reactive species with an unpaired electron 
What are the types of bond fission
. Homolytic fission - covalent bonds break and one electron goes to each atom forming to radicals
. Heterolytic fission - covalent bond breaks and both electrons go to the same atom form into ions
Draw a mechanism for free radical substitution including the reaction conditions
. Reaction condition-UV and high-temperature
. Initiation Cl2 —> ^UV Cl. +Cl.
. Propagation Cl. + CH4 —> .CH3 + HCL, .CH3 + Cl2 —> CH3Cl +Cl.
. Termination .CH3 + Cl. —> CH3Cl, .CH3 + CH3 —> CH3CH3, Cl. + Cl. —> Cl2 
What are the problems of free radical substitution
. Multi substitution occurs-overcome this by using excess alkane
. Mixtures of products form-they are unwanted bi products
. isomers-substitution occurs anywhere along the chain forming isomers
What is ozone and describe natural formation of O3
. Ozone found in the stratosphere
. I ozone absorbs UV radiation so UV at Earth surface is reduced
. O2.—>^UV O+O
. O2 + O —> O3
What are chlorofluorocarbons CFCs
. Contain chlorine fluorine and carbon all – all hydrogen is replaced
. They are stable, volatile, non-flammable and non-toxic
. Used in the past in aerosol cans, dry cleaning, air-conditioning, and fridges
. Not use anymore cause they destroy the ozone layer
What is the reaction occurring when CFC is enter the upper atmosphere
. Initiation Cf2Cl —>^UV CF2Cl. +Cl.
. Propagation Cl. + O3 —> O2 + ClO., ClO. + O —> O2 + Cl.
. Overall O3 + O —> 2O2
What is nitrogen oxides effect on the upper atmosphere and equation
. NO. Free radicals for nitrogen oxides, and destroy the ozone two
. NOI produced by thunderstorms, cart/aircraft engines
. Similar reaction as chlorine radicals
. NO. + O3 —> O2 + NO2
. NO2 + O —> O2 + NO.
. OVERALL O3 + O —> 2O2
What are the alternatives to CFCs
. Hydrochlorofluorocarbons (HCFC) and hydrofluorocarbons (HFCs) of being used until saferalternatives are developed
. HCFC is a broken down in the atmosphere more quickly
. HFC is broken down the atmosphere too they don’t contain chlorine and so don’t affect the ozone layer
. HCFCs and HFC are greenhouse gases
. Other alternatives include aerosols with pump spray/nitrogen components, fridges freezers using ammonia as the coolant gas, CO2 is used to make expanded polymers
what are the properties of alkenes?
. general formula CnH2n
. unsaturated hydrocarbons with at least one c=c functional group
. alkenes are more reactive than alkanes undergoing addition reactions
whatare sigma and pi bonds
. sigma bonds - end on ned overlap of orbitals directly between atoms (single bonds)
. Pi bonds- sideways overlap of P orbitals to give a Pi bond directly above and below (double bonds)
how many Pi and sigma bonds are present in double and triple bonds?
. double bond contains 1 sigma and 1 Pi
. triple bond contains 1 sigma and 2 Pi
what is the shape and rotation around a c atom in an alkene?
. trigonal planar shape around each atom in c=c bond
. no rotation around c=c bond as p orbitals must stay in the same position to overlap and form a Pi bond
. any c-c bonds will still rotate
what is stereoisomerism
. have the same structural formula but a different arrangement of atoms in space
what is the difference between E/Z isomerism
. Z is when both groups are on the same side _/
. E is when both groups are at either side
what is the Cahn-ingold-prelog priority rules
. it assigns priority to different atoms to name isomers
. atom with higher atomic number on each carbon is given higher priority
. in e isomers tehyll be positioned on opposite sides to eachother
. in z isomers theyll both be on the same side
what is the reactivity of alkenes?
. Pi bonds are weaker than sigma bonds
. Pi bonds break and electrons can be donated to form a bond
. invlved in reactios called addition reactions
. addition reactions have 100% economy
how do you synthesise a dihaloalkane?
. alkenes react with halogens to produce dihaloalkanes
. reaction conditions 20 degrees
. is halogenation
how do you synthesise a haloalkane?
. alkenes react with hydrogen halides to produce haloalkanes
. reaction conditions 20 degrees
. is an example of halogenation
how do you test for alkenes/ saturation?
. add bromine water solution and shake
. contains double bond - orange to colourless
. contains no double bond - no visible change
. bromine is added across the double bond
how do you syntehsise alkanes?
. alkanes react with hydrogen gas to produce alkanes
. reaction conditions Ni catalyst and 150 degrees
. is an example of hydrogenation
how do you synthesise alcohols
. alkenes react with steam to produce alcohols
. reaction conditions H3PO4 60-70atm and 300 degrees
. example of hydration
what happens to unsymmetrical alkenes in reactions?
. they can form isomers
. one of these isomers will be the most stable, this will be the major product and any less stable products wil be minor products
what determines carbocation stability?
. if its determined to multiple alkyl group, can be primary, secondary, or tertiary
what is an addition polymer?
. monomers are single repeating units
. polymers ar emade up of long repeating units of monomers
what is the reactivity of polymers?
. alkenes are unsaturated compunds
. polymers are saturated compounds
. polymers are chemically inert and not biodegradable
what casues polymer waste?
. polymers are unreactive so are not biodegradable
. this makes them long lasting and reusable but difficukt to dispose of
explain burying waste plastic?
. done when plastic is too difficult to separate
. not in sufficient quantities to make separation financially worthwhile
. too difficult technically to recycle
explain recycling plastics?
. we can sort plastics into different types
. polypropene can be melted and remoulded
. others can be cracked into monomers which can be used as organic feedstock to make more plastics/ chemicals
. overall process involves sorting and processing
explain burning waste plastics
. waste plastics can be burnt and the heat can be used to generte electricity
. toxic gases can be released
. passing through scrubbers containing NaHCO3 neutralises and removes the HCL
explain biodegradable/ photodegradable polymers
. made from materials such as starch and the hydrocarbon isopropene
. renewable raw materials wil not run out
. carbon neutral for plant based polymers
. plant based polymers save energy
wht are the properties of haloalkanes
. they are polar molecules due to the polar carbon-halogen bond
. halogens can be represented by an X symbol
polarity of haloalkanes
.polar molecule - halogen atom is more electronegative than the carbon atom thus withdraws eletron density from the carbon chlorine bond
. partially positive carbon can react with nucleophiles
what is a nucleophile?
. electron pair donor
. said to be a region of high electron density
. curly arrows represent movement of an electron pair
what is a substitution rection?
. involves swapping of nucleophiles and halogen atoms
. atom economy always less than 100%
what affects the rate of hydrolysis?
. depends on bond enthalpy of the carbon halogen bond
. weaker bonds break more easily and so reaact faster
what are the bond entahlpies of carbon halogen bonds?
. C-F - 467 KJmol
. C-Cl - 346 KJmol
. C-Br - 290 KJmol
. C-I - 228 KJmol
how can you compare the rate sof hydrolysis using H2O?
. add silver nitrate solution to the mixture
. silver ions react with halides as soon as they form, silver halide precipitate forms
. reaction is known as aqeous hydrolysis
. RX + H2O –> ROH + HX
what re the properties of alcohols?
. alcohols are polar molecules
. due to the electronegative hydroxyl groups which pull electrons in the C-OH bond away from the carbon atom
what are the boiling points of alcohols?
. alcohols have higher boiling points compared to alkanes
. alcohols are less volatile than alkanes of similar carbon atoms
explain hydrogen bonding in alcohols
. alcohols have hydrogen bonding between molecules
. alkanes have induced dipole dipole interactions between molecules
. hydrogen bonding is stronger and requires more nergy to overcome
explain the solubility of alcohols
. alcohols with short carbon chains are soluble in water
. alcohols and water molecules make hydrogen bonds with eachother
. alcohols make neutral solutions
. if there are more OH groups, there are more hydrogen bonds so the alcohol will be more soluble
link alcohol solubility to chain length
. the greater the carbon chain length the less soluble in water
. there are stronger induced dipole dipole interactions in longer carbon chains
. which break up hydrogen bonds between molecules
explain combustion reactions with alcohols
. alcohols can be oxidised by combustion
. they are good fuels with high enthalpies of combustion so produce a lot of energy per mole of alcohol burnt
. theyre added to petrol mixtures to prevent incoplete combustion as they contain an internal supply of oxygen in OH group
explain synthesis reactions of haloalkanes from alcohols
. synthesis of haloalkanes from alcohols
. alcohols will react with compunds that contain halides in a substitution reaction
. reaction conditions and reagents: NaBr H2SO4 and 20 degrees
explain elimination reactions in alcohols
. synthesis of alkenes from alcohols
. conditions and reagents: H2SO4 or H3PO4 and heat
. example of dehydration
explain oxidation reactions in primary alcohols
. heating a primary alcohol with potassium dichromate(VI) K2Cr2O7 solution and H2SO4 with distillation apparatus produces an aldehyde
. heating with excess oxidising agent and h2so4 under reflux produces a carboxylic acid
what happens to alcohols in oxidation reactions?
. heating an aldehyde with K2Cr2O7 and H2SO4 with reflux apparatus produces a carboxyllic acid and no water
What happens to secondary alcohols in oxidation reactions
. heating a secondary alcohol with excess oxidising agent and H2SO4 under reflux apparatus produces a ketone
what happens in oxidation of tertiary alcohols
. cannot be oxidised so no reaction
how do you test for alcohols?
. tertiary alcohols dont react with acidified K2Cr2O7
. this means they can be used to test between primary and secondary alcohols against tertiary alcohols
. add few drops of potassium dichromate (VI) and a few drops of concentrated H2SO4
. colour change from orange to green = primary and secondary alcohols
. no visible change in tertiary alcohols
draw reflux and distillation apparatus
nuh uh
when is distillation used?
. used to react substances and remove the product to prevent further reaction
when is reflux used?
. used to react volatile substances together to prevent substances from escaping
What is an electro file
Electron pair acceptor
What is redistillation
. Used to purify
. Select the fraction having the boiling point of a pure compound
. Draw a distillation apparatus
What is a Separating funnel and when is it used
. Products of a reaction of water is added to a separate Funnel whichis shaken and allowed to settle
.  less dense organic layer settles at the top
. Water soluble impurities dissolve in the lower aqueous layer
. Stop it he’s turned aqueous Layer is run off
What is a vacuum filtration
. When solids are filtered under vacuum
What is infrared spectroscopy
. Beam of infrared radiation passed through sample of chemical
. Bonds between different atoms absorb different frequencies of IR radiation
. IR radiation causes covalent bonds to vibrate more
. IR radiation that is not absorbed is detected by a detector
Explain how infrared radiation affect global warming
. Greenhouse gases in troposphere absorb readmitted IR radiation from earth
. This is real mood in all directions including back to earth
What are uses of IR spectroscopy
. Modern breathalysers use IR to look for presence of ethanol in breath by detecting OH bonds
. monitoring gases causing air pollution
When is mass spectroscopy used
. Determine abundance of isotopes in an element
. Can monitor breathing of patients under anaesthetic
. Testing for drug use in athletes/horses
. Analysing molecules in space
. Testing for toxic chemicals that may have contaminated marine life
