Module 4 - Keywords Flashcards
IUPAC nomenclature
international naming rules
organic compounds
carbon based compounds
general formula
the simplest algebraic formula of a member of a homologous series e.g. for an alkane: CnH(2n+1)
structural formula
the minimal detail that shows the arrangement of atoms in a molecule e.g. for butane: CH3CH2CH2CH3 or CH3(CH2)2CH3
displayed formula
the relative positioning of atoms and the bonds between them
skeletal formula
the simplified organic formula, shown by removing hydrogen atoms from alkyl chains, leaving just a carbon skeleton and associated functional groups
homologous series
the 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 the characteristic reactions of a compound
alkyl group
has the general formula CnH2n+1
aliphatic
a compound containing carbon and hydrogen joined together in straight chains, branched chains or non-aromatic chains
alicyclic
an aliphatic compound arranged in non-aromatic rings with or without side chains
aromatic
a compound containing a benzene ring
saturated
an organic compound containing single carbon-carbon bonds only
unsaturated
an organic compound containing multiple carbon-carbon bonds, including C=C, CΞC and/or aromatic rings
structural isomers
compounds with the same molecular formula but different structural formulae
homolytic fission
bond breaking where each bonding atom receive one electron from the bonded pair, forming two radicals
heterolytic fission
bond breaking where one bonding atom receives both electrons from the bonded pair forming a positive and negative ion
radical
a species with an unpaired electron
reaction mechanism
diagrams used to show clearly the movement of electron pairs with ‘curly arrows’ and relevant dipoles
σ - bonds
(sigma bonds) overlap of orbitals directly between the bonding atoms
complete combustion
a burning reaction where there is sufficient oxygen to oxidise the reagents completely
incomplete combustion
a burning reaction where there is insufficient oxygen to oxidise the reagents completely. The carbon/carbon dioxide formed
radical substitution
a reaction mechanism involving homolytic fission to produce radicals (initiation) followed propagation and termination
substitution
replacing on atom or group of atoms with another
π - bond
sideways overlap of adjacent p-orbitals above and below the bonding C atoms
stereoisomers
compounds with the same structural formula but with a different arrangement in space
E/Z isomers
stereoisomers which have two different groups attached to each carbon atom of the C=C group - CIP rules are used to prioritise groups
Cis-trans isomerism
stereoisomers which have two different groups attached to each carbon atom of the C=C group and the same group attached to each carbon atom
Cahn-Ingold-Prelog (CIP) priority rules
the rules used to identify the priorities in E and Z stereoisomers
Dihaloalkanes
a compound in which two of the H of an alkane have been replaced by halogens
Bromine water
bromine solution. Used to test for unsaturation (decolourised in unsaturated hydrocarbons)
Decolourised
the depth of colour is partially or completely removed
electophile
an electron pair acceptor
Markownikoff’s rule
predicts the most likely product of HX substitution reactions with unsymmetrical alkenes (He Who Has Hydrogen Gets Hydrogen)
Haloalkane
a compound in which one of the hydrogens of an alkane have been replaced by a halogen
carbocation
an organic cation
intermediate
a species which is produced in one step of a multistep reaction and then used up
polymerisation
monomers react together to make polymers
polymer
a long chain molecule with repeating units
addition polymer
polymer formed when unsaturated carbon molecules join to form polymers. These have 100% atom economy
sustainable
meeting the needs of today without impeding the needs of future generations
organic feedstock
an organic chemical that can be used as a raw material in the production of other materials
biodegradable
broken down by bacteria in the environment to produce non-harmful waste products
photodegradable
broken down by light in the environment to produce non-harmful waste products
fraction
a group of hydrocarbons with similar boiling points. They have similar properties so they have similar uses
fractional distillation
a method that uses differences in boiling points to separate crude oil into fractions
Describe the reactivity of alkanes.
- have a low reactivity w many reagents due to high bond enthalpy
- low porality of the σ - bonds present
- hence are insoluble in polar solvents (e.g. water) + form 2 layers
- C-H bond enthalpy: +415.5kJmol-1
What is the bond angle in alkanes?
109.5⁰
Describe the bonding in an alkane.
-saturated hydrocarbons containing single C-C bonds + C-H bonds as σ - bonds (single bonds) are free to move
Describe the trends in boiling points of hydrocarbons.
- as relative molecular mass increases
- longer chain length therefore
- more electrons present
- more points of surface contact
- more London forces
- more energy needed to break them so higher boiling point
Describe the effect on branching on the boiling point of hydrocarbons.
- fewer points of contact when branching
- fewer London forces between molecules
- reduced packing = fewer intermolecular (London) forces = lower boiling point
What causes a radical to form?
breaking a covalent bond
What are the stages of radical substitution? Describe them.
- initiation: homolytic fission of halogen molecule to form 2 radicals
- propagation: RADICALS ATTACK!, very rapid chain reaction which continues until no reactants remain
- termination: 2 free radicals combine to form a molecule
What is the equation for the iodination of ethane?
-initiation: I-I –> I• + I•
-propagation: C2H6 + I• –> HI +•C2H5
•C2H5 + I2 –> C2H5I + I•
-termination: I• + I• –> I2
I• + •C2H5 –> C2H5I
•C2H5I + •C2H5I –> C4H10
What conditions are necessary for radical substitution?
UV light
What is a sigma bond?
single bond, shared pair of 2 electrons, overlap of the s orbital
What is a pi bond?
sideways overlap of the p orbitals
What is a double bond made up of?
a sigma bond + a pi bond
Do pi bonds or sigma bonds have a higher bond enthalpy?
sigma
What is the bond angle and shape around the double bond of an alkene?
120⁰, trigonal planar shape, 3 regions of electron density around carbon repel equally, all atoms in the same place, hence trigonal planar shape
Describe the reactivity of alkenes.
- alkenes react easily as they have a C=C bond
- insoluble in polar substances (e.g. water) + form 2 layers
Describe the trends in boiling points of alkenes.
- BP increases with increasing chain length but BP of alkenes is lower than that of corresponding alkenes
- molecules can’t pack together as efficiently as in alkanes so there’s fewer intermolecular forces
What are the types of addition reactions that alkenes can take part in?
(2 molecules react to form 1 molecule, an unsaturated alkene becomes a saturated product)
- hydration
- hydrogenation
- halogenation
What are the conditions needed for hydrogenation?
- 150⁰C
- nickel catalyst
Describe the hydrogenation of ethene.
ethene + hydrogen –> ethane
Describe the halogenation of ethene and chlorine.
ethene + chlorine –> 1,2-dichloroethane
What are the conditions needed for hydration?
- H3PO4 (phosphoric acid) catalyst
- water as a gas
Describe the hydration of ethene.
ethene + water –> ethanol
How does hydrogenation affect a fat/oil (lipid)?
makes it more solid (less unsaturated..?)
Why is phosphoric acid used over other acids such as hydrochloric acid as a catalyst in hydration?
has more H+ ions
What is a mechanism?
a sequence of steps showing the path taken by electrons in an atom
What is a carbocation?
an organic ion in which a carbon atom has a positive charge
How do you show the movement of electrons in electrophilic addition?
curly arrows
Explain Markovinokov’s rule.
- He Who Has Hydrogen Gets Hydrogen
- when a compound HX is added to an unsymmetrical alkene, the hydrogen becomes attached to the carbon with the most hydrogen atoms attached to it
- happens this way around as intermediate carbocation formed is secondary + is more stable as it has 2 inductive effects
- primary carbocation made if carbon attached to centre of carbon atom + the halogen to the end one is less stable as it only has 1 inductive effect
