1.7 introductory organic chemistry Flashcards
1b: Complete 5 molecule drawings generated from the spreadsheet.
How many did you get right? Rank below:
1c: What is the difference between a hazard and a risk?
a risk is the likelihood of a hazard
2a: What is an alkane?
a saturated hydrocarbon (only has C and H with single bonds)
2a: What is the general formula of alkanes?
CnH2n+2
2b: What are isomers?
molecules with the same molecular formula but a different structural formula
2c: What are alkanes generally used for?
fuels
2c: Whence are alkanes obtained?
crude oil
2c: How is a certain alkane extracted from crude oil? (2)
fractional distillation
cracking and reformation
2d: Why are alkanes a good source of fuel? (2)
provide a lot of energy
we already have the methods and equipment
2d: Why should we have alternative sources of fuel besides alkanes? (2)
non-renewable source (crude oil)
CO2 produced from combustion, affecting climate change
2e: What are the products of combustion of a hydrocarbon? (2)
CO2, H2O
2e: What is a free radical?
an unstable molecule
2e: Name the stages of free radical substitution. (3)
initiation
propagation
termination
2e: Describe the initiation stage of free radical substitution (halogen + alkane).
one C-H bond splits, making the hydrocarbon a radical (e.g. CH3CH3 -> CH3CH2. + H.)
2e: Describe the propagation stage of free radical substitution (halogen + alkane).
one of the halogen atoms breaks off and joins onto the hydrocarbon radical (e.g. CH3CH2. + Cl2 -> CH3CH2Cl + Cl.)
2e: Describe the termination stage of free radical substitution (halogen + alkane).
every radical joins with another radical until there is none left (e.g. Cl. + H. -> HCl)
2e: How do you represent the movement of an electron when drawing the mechanism of a free radical reaction?
a single-headed curly arrow from the bond to an atom
2e: Why does a free radical reaction have more products than expected?
the radicals can join onto any other radical, so for example the substitution of chlorine into ethane can also give butane and hydrogen as well as chloroethane and HCl
3a: What is the general formula of alkenes?
CnH2n
3a: What is an alkene?
an unsaturated hydrocarbon with one carbon-carbon double bond
3a: Describe the structure of a double bond.
consists of a pi bond (single covalent bond between two sp3 orbitals) and a sigma bond (between two p orbitals; they bend to create arcs either side of the pi bond)
3b: Describe cis-trans isomerism.
in a cis molecule, the heaviest groups (e.g. methyl, ethyl) are both on the same side of the double bond; they are opposite in a trans molecule
3b: Why does cis-trans isomerism occur?
restrictive rotation (the C=C double bond cannot rotate)
3c: Describe E-Z isomerism.
similar to cis-trans; comes into effect when atoms besides C and H are involved - E = opposite, Z = same - and is decided by atomic number
3di: addition CnH2n + H2 ->
an alkene + hydrogen goes to… with catalyst…
CnH2n+2
an alkane; catalyst Ni
3dii: addition CnH2n + F2 ->
an alkene + halogen goes to…
CnH2nF2
a di-sub halogenoalkane
3diii: addition CnH2n + HCl ->
an alkene + hydrogen halide goes to…
CnH2n+1Cl
a mono-sub halogenoalkane
3div: addition CnH2n + O2 ->
an alkene + oxygen goes to… with catalyst…
CnH2n(OH)2
a diol; catalyst K2MnO4
3ei: Identify and describe the mechanism of the reaction between HBr and C2H4
electrophilic addition
HBr is polarised, so H end is pulled towards the double bond in ethene
this takes out an electron, creating a Br. radical
the H joins to the ethene, creating an ethyl radical
eventually a Br. radical attaches to the ethyl
3ei: Identify and describe the mechanism of the reaction between Br2 and C2H4
electrophilic addition
Br2 becomes polarised near the double bond
the delta+ end pulls an electron from the bond
the Br-Br bond splits, creating a Br. radical and C2H4Br. radical
these eventually join
3eii: In one stage of an electrophilic addition reaction between H. and .CH2.CHCH2, where does the H. join on and why?
the one at the end; it is less stable as there are fewer nearby covalent bonds to provide stability
3f: Describe the test for a C=C bond.
bromine water: orange -> colourless
3f: What is the equation of the test for a C=C bond (using ethene an asn example)?
C2H4 + 1/2Br2 + OH -> C2H4BrOH
3g: Describe the mechanism of addition polymerisation.
initiator Q-Q splits to give Q. Q.
Q. interacts with CnH2n to split the double bond and create a .CnH2nQ radical
this reacts with another CnH2n and so on to create a chain
eventually the other Q. reacts with the end of the chain to finish the reaction
