Mod 4 organic chem Flashcards
hydrocarbons
compound containing hydrogen and carbon ONLY
Homologous series
family of compounds with similar chemical properties & functional group whose successive members differ by CH2
functional groups
OH - alcohol (ol)
COOH - carboxyllic acid
C=O in middle ketone (one)
C=O at end aldehyde (al)
types of hydrocarbons
aliphatic- straight chain
alicyclic- joined in ring structures
aromatic- some or all atoms found in benzene ring (smell nice)
formulae
empirical- simplist whole number ratio
general - formula for any homologous group eg CnH2n
displayed formula- drawed version showing all Cs&Hs
structural- writing it as you go along CH3CH2CH3
skeletal - lines without including C OR H
Structural isomerism
Compounds with the same molecular formula but different structural formula
-branched
-positional (CH3 going on different carbon)
-functional- make different functional group
eg ketone - aldehyde
Types of bond fission
homolytic- when a covalent bond breaks each of the bonded atoms takes one of the shared bonded pair of electrons from the bond (forms 2 radicals)
heterolytic- when a covalent bond breaks one of the bonded atoms takes both of the electrons from the bond
types of reaction
addition- adding something going from 2 products to 1
elimination- taking something out in a reaction going from 1 to 2 products
substitution- swapping something out for another thing
Alkanes
-sigma bonds
-saturated
-109.5
-CnH2n+2
chain length affect on bp
longer the chain the higher the boiling point
-more london forces
-stronger bonds
-harder to overcome
branching effect on bp
more branching= lower bp
-less surface area of contact
-weaker london forces
easier to overcome
(branches get in the way preventing the branched molecules getting as close together)
reactivity of alkanes
C-C & C-H bonds are strong
C-C bonds are non polar
C-H bonds have similar electronegativities that they are considered non - polar
combustion of alkanes
complete- plentiful oxygen
incomplete- not enough oxygen (carbon monoxide formed) toxic CO
CH4 + O2 –> CO2 + H2O
Free radical substitution
initiation- UV light causes covalent bond to break by homolytic fission
propagation- chain reaction reacts with radical then reacts with compound (BR2)
termination- 3 equations putting all radicals together to make 3 compounds
Alkene to haloalkane
Hydrogen halide addition
H-Br
Alkene to alkane
hydrogenation, adding H2 (nickel catalyst needed)
Alkenes
unsaturated hydrocarbons
-formula = CnH2n
120 degrees shape
sterioisomerism
-Same structural formula but different arrangements of atoms in space
E- egyptian trans
Z- zame zide cis
cis/trans - must have at least 2 hydrogens
Cahn-Ingold-prelog
atom with highest atomic number has priority
compete atoms together then can decide if E/Z isomerism
Reactivity of alkenes
alkenes are MORE reactive than alkanes as alkenes contain pi bonds which is broken more relatively
addition reactions of alkenes
-hydrogen + (nickel catalyst)
-halogens
-hydrogen halides
-steam in the presence of an acid catalyst (OH)
electrophillic addition
double bond breaks giving pair of electrons to H
-H then bonds to the compound
-carbocation is formed
-halide (delta neg) reacts with carbocation causing it to join on
Markownikoffs rule
2 isomers formed
- the carbocations will be either a major or minor
minor = primary/secondary
major = secondary/tertiary
carbocation stability
stability increases from primary - tertiary
charge is spread out to alkyl groups so more groups more stable
examples of polymers
polypropene - childrens toys
polystyrene - used for packaging material
polytetrafluoroethene - used as coating for non-stick pans
disposing polymers
Landfill- dumping ground for waste
+waste doesnt need sorted
-affects wildlife
combustion- burning in O2
+produce power for homes
-may produce carbon monoxide
types of polymers
biodegradable polymers- break down after its intended purpose
-expensive
bioplastics- produced from starch, cellulose etc
-expensive
photodegradable- broken down by light
-expensive
-no harmful chem produced
Haloalkane to alcohol
NaOH (aq) under reflux
sodium hydroxide
Alcohols
properties
- O-H bond is polar
-most alcohols soluble in water as they form hydrogen bonds
-low volatility
-higher boiling points as hydrogen bonds are stronger
(harder to overcome)
Alcohol to haloalkane
Sodium halide and H2SO4 catalyst
dehydration of alcohols
water molecule removed and alkene now made C=C
H3PO4 needed
classifying alcohols
primary- when the -OH group is attached to a carbon atom that is attached to 2 hydrogens
secondary - the -OH is attached to a carbon that is attached to 2 alkyl groups and a hydrogen
tertiary- when the -OH group is attcahed to 3 alkyl groups
Oxidation of primary alcohols
with acidified potassium dichromate (K2Cr2O7)
heated and distilled = aldehyde
heated under reflux = carboxyllic acid
orange to green
oxidation of secondary alcohols
using acidified dichromate
oxidised to ketones no further
orange to green
oxidation of tertiary alcohols
tertiary alcohols do not oxidise
acidified dichromate remains orange
substitution of alcohols
alcohols react with hydrogen halides to form haloalkanes
propan-2-ol + HBr –> C3H7Br + H2O
(dehydration)
hydrogenation
reaction where hydrogen is added across double bond
-alkenes to alkanes
double bond breaks then hydrogen takes the pair of electrons and passes them onto the other hydrogen
-first hydrogen attaches to make carbocation
then carbocation reacts with hydrogen to make alkane
CONDITIONS- high temp and nickel catalyst
electrophiles & nucleophiles
electrophiles- electron pair acceptors
nucleophiles- electron pair donors
esterification of alcohols
Carboxylic acid + alcohol – ester + water
OH comes off carboxylic acid & H comes off alcohol to make H2O
-alkyl chain (from alcohol)
-oate from carboxylic acid
COOCH3
Heating under reflux
round bottom flask
condenser
rubber tubing
stand and clamp
heat source
Spectroscopy
Used to identify the molecular mass of an organic compound and to gain further information about its structure
what are fragment ions
when in mass spectrometer it loses electrons forming positive ions
-detects the mass to charge ratio (m/z)
types of fragment ions
CH3+ = 15
C2H5+ = 29
C3H7+ = 43
OH- = 17
CH3CH2O+ = 45
Mr from a mass spectra graph
The furthest line to the right
except the very small one that will be carbon-13 so doesn’t count
Calculating carbon atoms
height of M+1 peak / height of M peak (x100)
wavelength numbers
haloalkanes = 500-800
alkanes = 750-1100
alkenes = 1630-1680
C=O bond = 1630-1820 (1700)
carboxylic acids = 2500-3300 (broad) and sharp dip
alcohols = 3200-3600 broad round shape
application of infrared spectroscopy
alcohol breathalyser
analyse vehicle emissions (carbon monoxide etc)
Ozone layer
found at the outer edge of the stratosphere varies from 10-40km above earths surface
O3 layer
-CFCs deplete the ozone layer
CFCs uses
In refrigerants, air conditioning units and as aerosol propellants
