Module 4 Flashcards
Empirical formula
Simplest whole number ratio of elements in a compound
Molecular formula
The actual number of atoms of each element in a compound
General formula
Formula which covers a homologous series
Structural formula
Minimal level of detail needed to draw something
Displayed formula
Shows all of bonds
What is the priority list of order for iupac namunclature
- Carboxylic acid, aldehyde,ketone,alkene, alcohol, halogen
Homologous group
- compounds with same functional group
- but each successive member differs by ch2
Functional group
part of molecule responsible for its chemical reactions
hydrocarbon
molecule containing carbon and hydrogen only
saturated compound
contains single bonds only
unsaturated compound
contains atleast one carbon to carbon multiple bond
aromatic
contains a benzene ring
aliphatic
contains carbon in a straight chain, branched chain or non-aromatic ring
structural isomer
compounds with same molecular formula but different structural formula
stereoisomerism
compounds with same structural formula but different arrangement of atoms in space
homolytic fission
where covalent bond breaks and electrons go to each atom forming 2 radicals
heterolytic fission
covalent bond breaks and both electrons go to one atom forming 2 ions
radical
highly reactive species with an unpaired electron
curly arrow
shows movement of pair of electrons
nucleophile
electron pair donor
electrophile
electron pair acceptor
describe bonding in alkanes
-sigma bonds
- which can rotate and are formed by head on overlap of neighbouring p-orbitals
what is the shape in alkanes?
tetrahedral shape 109.5
why do increased chain lengths increase boiling point in alkanes?
- increased chain length increases number of carbons
- increased points of surface contact
- so stronger induced dipole dipole interactions between molecules
- which needs more energy to overcome
why does increased branching decrease boiling point in alkanes?
- increased branching decreases points of surface contact between molecules
- weaker induced dipole dipole interactions between molecules
- which needs less energy to overcome
Why are alkanes very unreactive?
- due to high bond enthalpies
- and low polarity of C-C and C-H
why are alkanes used as fuels?
- as large amount of energy is released with bond breaking
what are the products of complete combustion?
- CO2 and H2O
what are the products of incomplete combustion?
- CO and H2O
- Carbon dioxide and carbon
- CO is poisonous
- CO2 and H2O are greenhouse gases
what is needed for alkane and halokane to react
- Halogen
- UV light
- High temp
What is the mechanism called of halogen and alkane reaction
- free radical substitution
What are the limitations of free radical substitution?
- multi substitution can occur
- substitution occurs at different positions on carbon chain producing mixture of isomers
why are alkenes reactive
- has sigma bond which is stronger and weaker pi bond which restricts rotation
- during reactions weaker pi bond breaks and stronger sigma bond remains intact
what is shape around alkene?
trigonal planar- 120 degrees
describe bonding in alkene
- sideways overlap of 2 p orbitals on each carbon forms a pi bond above and below the plane of the molecule
When can a molecule exhibit e/z isomerism?
if it has:
- a carbon carbon double bond which restricts rotation
- has 2 different groups attached to each carbon in carbon carbon double bond
when can molecule exhibit cis/trans isomerism?
- when 2 substituents are the same on each carbon (one on each)
what is percentage atom economy for addition reactions?
- 100%
Why are addition polymers non biodegradable?
- they have strong C-C bonds
How to deal with addition polymers?
- separate into types by sorting and recycle
- crack them into monomers and use them as feedstock for other reactions
- burn waste to generate electricity
- landfill
why is pentan-2,2-diol more soluble than pentan-1-ol?
pentan-2,2-diol has more hydroxy groups and so forms more hydrogen bonds with water
why are haloalkanes polar
- the halogen is more electronegative than the carbon
how to measure rate of hydrolysis
- heat haloalkane with water in presence of silver nitrate in ethanol
- silver ion reacts with the halide ion to form a coloured ppt
- measure time taken
why is C-I faster rate of hydrolysis than C-Br
- Bond enthalpy of C-I is weaker than C-Br so breaks more easily and so faster hydrolysis
how is conc of ozone maintained in atmosphere?
O3->O2+O
reversible reaction
uses of CFCs eg Cl3FC
refrigerants, dry cleaning fluids, aerosol propellants
useful properties of CFCs
-low reactivity
- non-toxic
-non-flammable
-volatile
why are CFCs bad?
- produce chlorine radicals which catalyse destruction of ozone
why is ozone good
- absorbs UV light from atmosphere
how to purify liquid sample:
- add base to neutralise acid
- transfer contents to separating funnel and shake
- less dense layer at top and more dense at bottom
- run of required layer
- dry organic layer with MgSO4
- redistill the liquid to further purify it and collect
how does ir spectroscopy work
- molecules absorb ir radiation
- make bonds vibrate
green house gases such as ch4 and co2 and h2o absorb ir radiation
causes global warming
uses of ir spectroscopy
- monitor gases causing air pollution
- modern breathalysers to monitor ethanol
