3.3.1 Introduction to organic chemistry Flashcards
what is the impirical formula ?
Simplest whole-number ratio of atoms of each element in a compound
what is a homologus series
a series of compounds w same general formula
- they have same general formula that defines the compounds properties
- they show a gradual variation in physical properties, eg their boiling points.
-they have similar chemical properties
what is a molecular formula
formula that tells you the actual number of atoms of the element in a compound
each of the type of formulas
displayed formula - c-h-c (fully drawn out formula)
structural formula= CH3CH2CH3
which free radical initiation produces which
homolytic fission produces 2 free radicals , in a 2cl out comes 2 cl free radicals
in Heterolytic fission ions are produced
what is a free radical
a reactive species which possess an unpaired electron, no charge
which form of fission is more common
Most organic reactions occur via heterolytic fission, producing ions
what is structural isomerism
compounds with same molecular formula different structures (or structural formulae
what types of structural isomerism is there
*Chain isomerism - Compounds with the same molecular formula but different structures of the carbon skeleton
*Position isomerism - Compounds with the same molecular formula but different structures due to different positions of the same functional group on the same carbon skeleton
*Functional group isomerism- Compounds with the same molecular formula but with atoms arranged to give different functional groups
what is a stereoisomer
molecules with the same structural formula but the atoms are arranged differently in space
difference between trans and cis isomers
Cis isomers have the hydrogens on the same side of the carbon
trans isomers have the hydrogens on the opposite sides of the carbon
what has to happen to have trans/cis isomers
each carbon atom must be bonded to 2 diff groups , on one side a carbon cant be bonded to H and H
but each carbon must be bonded to min 1 hydrogen
whats an alkane
Alkanes are saturated hydrocarbons.
fractional distillation
Oil is vapourised then passed into column.
* The fractions condense at different heights *
* The bottom hotter
* The separation depends on boiling point.
* boiling point depends on size of molecules.
* The larger the molecule= larger van der waals forces
* Similar molecules (size, bp, mass) condense together
* Small molecules condense at the top at lower temperatures
what is cracking
conversion of large hydrocarbons to smaller hydrocarbon molecules by breakage of C-C bonds
which cracking produces a high percentage of alkenes
Thermal cracking produces a higher percentage of alkenes
catalytic cracking
.Catalytic cracking happens at a slight pressure, high temperature (450)
.with a zeolite catalyst
. used mainly to produce motor fuels +aromatic hydrocarbons , produces branched and cyclic hydrocarbons too
what is zeolite catalyst made of
(sodium aluminate and sodium silicate.)
thermal cracking
high temp +pressure (7000KPA and 400-900C)
produces just mainly alkenes
Economic reasons for cracking
.The petroleum fractions with shorter C chains (e.g. petrol and naphtha)in more demand than larger fractions.
- To make use of excess larger hydrocarbons and to supply demand for shorter ones, longer hydrocarbons are cracked.
- The products of cracking are more valuable than the starting materials(e.g. ethene used to make poly(ethene),branched alkanes for motor fuels,
how are alkanes used as fuels
releases heat energy when burnt
Alkanes readily burn in the presence of oxygen. This combustion of alkanes is highly exothermic,
incomplete combustion produces less energy per mole
the pollutants and why they’re bad
Nitrogen oxides-NO is toxic and can form acidic gas NO2 NO2is toxic and acidic and forms acid rain
Carbon monoxide- toxic and contributes to respiratory problems
Unburnt hydrocarbons- Contributes towards formation of smog
soot(carbon)- Global dimming and respiratory problems
what are the potential products of incomplete combustion
Co or C + H2O
sulfur dioxide -
Sulfur containing impurities are found in petroleum fractions which produce SO2 when they are burned.
SO2 dissolve in atmospheric water and can produce acid rain - damage environment + erodes + damages buildings
coal also high in SO2
Flue -gas desulphurisation -
calcium oxide -SO2 + CaO to form CaSO3 then reacted on to form calcium sulphate (CaSO4) - Gypsum - used in plastering so money made from the waste products
catalytic converters
cross section mesh of Platinum or Rh (large SA)
2CO + 2NO —> 2CO2 +N2
2NO —> N2 + O2
or even the NO reacted with more unburnt hydrocarbon to form N2 CO2 and H20
in nomenclature what applies as a methyl ethyl group
a methyl group only applies in nomenclature if its not on the end of the carbon chain , there must be a carbon either side to it - a methyl group cannot be on the endeg:
C-C-CH3- C
