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 aren’t 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