module 7 HSC Flashcards
molecular geometry of triple bonded carbon
linear
molecular geometry of double bonded carbon
trigonal planar
molecular geometry of single bonded carbon
tetrahedral
alkane
- saturated
- single bond
alkene
- unsaturated
- double bond
alkyne
- unsaturated
- triple bond
structural isomer
compounds with the same molecular formula but different molecular structures
- chain
- position
- functional group
chain isomers
reaarange the carbon backbone
position isomer
changing the position of the functional group on the carbon backbone
functional group isomer
change the functional group
stable out of alkane, alkene, alkyne
alkane = stable
alkyne + alkene = relatively unstable
intermolecular bonds = single covalent bonds are more stable as triple and double have pi bonds which make them more vulnerable (hug easier to break than a handshake)
- pi bonds are more exposed to chemical reagents as they are above and below bonding atoms
- beta bonds arenāt as exposed to chemical reagents as they are between bonding atoms
bond stability
ease or difficulty of another molecule reacting with the molecule
bond strength
energy input required to completely dissociate two atoms joined by a particular bond
strength out of alkane, alkene, alkyne
alkane < alkene < alkyne
boiling point of alkanes
- intermolecular forces of dispersion forces
- as the chain length increases , strength of dispersion forces increase which leads to increase boiling points
- branched chain isomers = smaller surface area + more compact shape -> reduced opportunity for temporary dipoles and has weaker dispersion forces leading to lower boiling points that straight chained isomers
types of addition reactions
- hydrogenation
- halogenation
- hydrohalogenation
- hydration
what molecule is addition reactions for
unsaturated
hydrogenation
alkenes:
alkene + H2 -> alkane
catalyst: Pd/c
alkynes:
alkyne + H2 -> alkene
catalyst: lindlar catalyst poisoned with Pb (for alkene as final product)
halogenation
alkene + X2 -> ..
- the two halogens get added across the bond
- eg. chlorination, bromination, iodination
- molar ratio is important if 2Br2 then add 4
hydrohalogenation
HX added across the pi bond
eg. hydrobromination
hydration
alkene:
alkene + H2O -> alcohol
catalyst: dil. H2SO4 + heat
- markovnikovs rule applies
alkyne:
alkyne + H2O -> keytone/aldehyde but prioritise keytone if possible
markovnikovs rule
hydrogen will bind to carbon tom with a greater number of hydrogen already attached to it
substitution reaction
alkane + Cl2 -> add and forms chlroalkane + HCl
requires UV light
combustion of alcohol
alcohol + O2 -> CO2 + H2O
- extremely exothermic
complete:
- sufficient oxygen
- all carbons converted to CO2
incomplete:
- oxygen deficient
- some carbon released as CO or soot
coefficient of fuel in combustion
always 1
dehydration of alcohols
alcohol -> alkene + H2O
catalyst:
- conc H2SO4
- heat for primary and secondary
- RTP for tertiary
alcohol substitution with hydrogen halide
alcohol + HX -> haloalkane + H2O
- catalyst: ZnX2
eg. if it was chlorine it would be ZnCl2
reactivity of hydrohalides
HI > HBR > HCl > HF
oxidation of alcohols
primary: aldehyde -> carboxylic acid
secondary: ketone
tertiary: does not occur
catalysts:
- heat
- KMnO4 , acidified potassium permanganate
or K2Cr2O7, acidified potassium dichromate
- dil H2SO4
learn redox
substitution of haloalkane
primary + secondary:
catalyst: heat, acetone solvent
haloalkane + dilute NaOH -> alcohol + salt
eg. bromoethane + NaOH -> NaBr + ethanol
tertiary:
tertiary haloalkane + H2O -> tertiary alcohol + HX
catalyst: heat
hydroxyl bond info
- polar covalent due to the large electronegativity differences
boiling point trends: alcohol vs alkane
- as the chain length increases, stronger dispersion forces = higher bp for both
- alcohols > alkanes
- alkanes = non-polar -> only dispersion forces
- alcohols = polar -> dispersion, hydrogen bonding, dipole-dipole
- harder to break - as length increases from 1-8 , alcohol is still greater
- but the difference is smaller
- proportion of non polar bonds in the alkyl chain and polar bonds diminishes making dispersion forces the dominating force
difference in boiling points of alcohols
1 > 2 > 3
- since -OH in primary is the most accessible, dipole-dipole + hydrogen bonding is stronger
- crowding of the -OH group also hinders he formation of hydrogen bonds
formation of amine
alcohol + ammonia -> primary amine + water
difference between amine and amide
amine = N and formed from alcohol
amide = carbonyl group attached to the N , produced throuh condensation reaction of carboxylic acids
production of amides
primary amide:
carboxylic acid + ammonia -> primary amide + water
catalyst:
- reflux
- DCC
- 190 degrees celcius + 4 hours
secondary amide:
carboxylic acid + primary amide -> secondary amide + water
catalyst:
- reflux
- DCC
- 190 degrees celcius + 4 hours
tertiary amide:
carboxylic acid + secondary amide -> secondary amide + water
catalyst:
- reflux
- DCC
- 190 degrees celcius + 4 hours
dissolving of alcohols in water
- break solvent -solvent
- break solute - solute
- form solute -solvent
due to the alcohols polar head, it dissolves readily in polar solvents such as water in comparison to alkanes but less in non-polar solvents such as benzene
solubility trends in alcohols
- increased carbon chain = increased solubility of alcohols in polar solvents
tertiary > secondary > primary
- since tertiary is the most compact with the least accessible Oh it has the weakest dispersion forces and solute-solute interactions
natural sources of hydrocarbons + disadvantages and advantages of petroleum
fossil fuels: produced by natural processes on fossilised remains of organisms over significant time
- NON RENEWABLE
- eg. petroleum
advantages: - environmental: extraction reduces pressure on underground oil reservoir to minimise oil seeping
- economic: cheap to extract as fossil fuels are found readily
- sociocultural: creates new communities where there are more job opportunities
disadvantages:
- environmental: drilling and fracking damages land, exposing heavy metals and radioactive substances
- economic: requires relatively high initial cost and infrastructure
- sociocultural: may intrude on scared indigenous land, degrade appeal of natural tourist attractions
advantages and disadvantages of hydrocarbon uses
a:
- environmental: natural gas burns cleaner than wood, haber process saves habitat from conversion into cropland
- economic: provide more employment, taxation revenue generated
- sociocultural: cultural globalisation with increased international travel, increased availability of electricity boosting community
d:
- environmental: acid rain from NO2, climate change caused by CO2 production and runaway greenhouse effect
- economical: global wealth inequality, automation leads to less jobs in manual labour
- sociocultural: degrade appeal of tourist attractions, human rights violations in extreme cases
biofuels
renewable fuels derived from plant material due to fossil fuels depleting rapidly and the rapid pace of climate change
- eg. sugarcane, grains
- carbon neutral = no net release of CO2
eg. bioethanol, biogas, biodiesel
advantages and disadvantages of biofuels
a:
- renewable
- carbon neutral
- when bioethanol is used it burns more cleanly which reduced the release of carbon monoxide and mitigates the need for toxic additives
d:
- relatively new
- expensive
- requires environmental sacrifices to maximise fuel yield
- deforestation which destroys the habitat
- lots of energy required
evaluation: while there is an absolute imperative to develop biofuels further, they have not been widely accepted into common usage due to their economic and political unviability at this point in time
bioethanol
- produced from fermentation of glucose
a:
- carbon neutral -> CO2 emitted from complete combustion is matched to the amount of CO2 consumed by sugarcane in photosynthesis
d:
- requires expensive modifications
- additional CO2 is emitted in processing and transportation
- ethanol is lower enthalpy of combustion ithan octane but requires more fuel to make the same energy
fermentation
biological process by which carbohydrates are converted to alcohol by yeasts and other microorgansisms
conditions of fermentation
- zymase enzyme
- 37 degree temperature
- anaerobic environment (deprived of oxygen)
- low pH (3.7 - 4.6)
photosynthesis
6CO2 + 6H2O -> C6H12O6 + 6O2
fermentation of glucose
C6H12O6 -> (zymase) 2C2H5OH + 2CO2
combustion of bioethanol
C2H5OH + 3O2 -> 2CO2 + 3H2O
properties of aldehydes and ketones
carbonyl group
- oxygen is more electronegative than carbon so C-O is polar
- has dispersion + dipole
- weaker intermolecular forces than alcohols and they lack the ability to have hydrogen bonding
- solubility decreases as the chain length decreases
enthalpy of combustion in alcohol discussion
factors that increase delta H of combustion:
- not stirring water at the base of the can which is warmer ā> stir vigorously with. rod
- thermometer resting at the base of the can which may be warmer -> suspend the thermometer in the water with a clamp from the retort stand
factors that increase delta H of combustion:
- impurities in water so it wont combust well -> change spirit burner
- can is too far from flame or has soot so there is insufficient heat transfer -> clean can and move closer
- can is too close to the flame so there is insufficient O2 and incomplete combustion occurs -> move further away
- heat radiated/conducted from apparatus and surroundings -> turn off fans and use a lid
properties of carboxylic acids
- polar: presence of two highly electronegative oxygen atoms
- has dispersion + hydrogen + dipole
- stronger intermolecular forces than alcohols as it has both CO and OH
- high boiling points and high solubility (shorter)
- the longer the chain, the non-polar portion dominates making it less soluble
properties of amines
polar as the nitrogen is highly electronegative
- has both dipole dipole and hydrogen bonding but weaker than an OH bond as the difference i smaller
- weaker intermolecular forces than alcohols and carboxylic acids
- stronger than alkanes
- soluble in water esp short chained
- high boiling point than alkane but lower than carboxylic and alcohols
tertiary < secondary < primary (more hydrogen bonds) and tertiary does not participate in hydrogen bonds -> lower solubility and boiling point
amides
primary and scondary have hydrogen bnding
- all have dipole dipole
- strongest intermolecular forces out of all organic compounds due to the unique geometry in the hydrogen bonding
- high boiling points
smaller amides are more soluble as dispersion forces decrease as molecular weight increases
what is the safety sheet called
Materials Safety Data Sheet (MSDS) or Safety Data Sheet (SDS)
how does MSDS/SDS protect
- potential hazards
- precautions to avoid injury
- first aid action plan
dangers that organic substances pose
- volatile (vapour at rtp)
- flammable
- corrosive/caustic
how to safely use organic substances
personal protective equipment (PPE)
- safety goggles
- gloves
- lab coat
- fume cupboard to handle volatile substances
- emergency shower + eye washer
benzene
C6H6
- ring structure
- aromatic
- alternating double and single bonds
- extremely stable
phenols
basically benzene with a hydroxyl group that replaces a hydrogen atom
- weakly acidic
esters
-COO
- equilibrium reaction
alcohol + carboxylic acid ->-< ester + water
catalyst:
- conc. H2SO4
- reflux
scents of esters
ethyl butanoate = pineapple
ethyl ethanoate = nail polish rem
properties of esters
- two polar bonds C-O and CāO
- dipole dipole and dispersion forces
- lack of hydrogen bonding -> lower boiling point and poor solubility
- as the chain increases = stronger dispersion forces
- solubility decreases as chain increases and hydrophobic chain dominates
production of esters
conc H2SO4 increases rate of reaction and acts as a dehydrating agent shifting equilibrium right
- heat increases the rate of reaction
- boiling chips prompts even boiling and controls boiling
reflux
procedure by which flask is continually heated whist vapours eerging from it are guided through a condenser tube which cools the gases and condenses them back into the reaction flask
role of H2SO4 in esters
acts as a catalyst to increase rate of reactions
acts as a dehydrating agent to shift the equilibrium to the right
role of reflux for esters
- prevents loss of reagents and products
- allows reaction to be performed at a much higher temperature
- improves safety
role of boiling chips
- provides nucleation points for bubbles to promote a smoother boil
- reduces risk of superheating
surfactants + example
surface-active agents which lower the surface tension of a liquid
- hydrophilic head
- hydrophobic tail
= non-polar alkyl tail
eg. soaps and detergent which are added to clean non-polar substances from surfaces such as oil and grease
natural vs artificial vs artificial soaps and detergent
soap = natural
detergent = artfiicial
hydrophilic head
- polar
- often charged
- interacting with water molecules by ion-dipole interactions and hydrogen bonding
hydrophobic tail
- non-polar
- does not interact strongly with water
- interacts with other alkyl tails via dispersion forces
soap
ion with a long non-polar alkyl tail and a polar charged carboxylate head
- present as sodium/potassium salts
hardwater:
- precipitates with Mg2+ and Ca2+ to form scum
anionic detergent
- ion with long non-polar alkyl tail and polar anionic sulfate head
- present as sodium/potassium salts
- good lather = dishwashing, laundry detergent
- too strong for personal hygiene
hardwater:
- forms soluble complexes with Mg2+ and Ca2+
- no scum but efficacy decreased ā> solved with phosphate buffers
cationic detergent
- ion with non-polar alkyl tail and a polar cationic trimethylammonium head
- present as chloride or bromide salts
- not as harsh as anionic
- shampoo and antiseptics, disinfectants
- reduces tangling
- biocidal - kills microorganisms
hardwater:
- no effect
- positively charge
biocidal
kills microorganisms
non-ionic detergent
- molecule with non-polar alkyl tail and polar repeating polyethylene glycol head
- always end in OH
- uncharged head but still polar
- less lather
- shampoo conditioner
hardwater:
- no effect, neutral so it doesnt react
hard water
impure water that contains Ca2+ and Mg2+
micelles
spherical arrangements of surfactant molecules with hydrophobic tails trailing centre and hydrophillic heads facing outwards
question structure for soaps
- structure: hydrophilic polar head + hydrophobic tail non polar
- surfactant dissolves in water
- orientation: surfactant molecules align themselves such that the non-polar alkyl tails stick into the substances forming dispersion forces and the polar heads face outwards forming ion dipole forces with the water
- agitation: when surface is agitated, through virgourous scrubbing, small droplets of greae are lifted off the surface and momentarily suspended in water where incomplete micelles form with the polar heads facing outwards and on-polar tails sticking to the oil
- as oil droplets become smaller complete micelles are formed
- micelles repel each other by their spherical outer surface of negative charges and disperse throughout the water
- emulsification , electrostatic repulsion stops the oils from coming together, but two immiscible liquids are made to mix by the action of the emulsifier
- drained away
