4.1 basic organic chem Flashcards
define nomenclature
system of naming compounds
what is a homologous series? give 3 examples
series fo substances with the same functional group and the successive members only differing by a CH₂ unit.
eg. alkanes, alkenes and alcohols
what is an alkane?
a saturated hydrocarbon
what is the alkane general formula?
CnH2n+2
name the first 10 alkanes
methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane
define an aliphatic hydrocarbon
a hydrocarbon in which carbon atoms are joined in a straight chain or branched chains
define an alicyclic hydrocarbon
a hydrocarbon that is an aliphatic compound arranged in non-aromatic rings with or without side chains
(no benzene rings, still ring structure)
define aromatic hydrocarbon
a compound with a benzene ring
define general formula
an algebraic formula that can generate any molecular formula in a family.
eg. CnH2n+2
define empirical formula
simplest whole number ratio of atoms of each element in a compound.
eg. C2H6 –> CH3
define molecular formula
the actual number of atoms of each element in a compound
define structural formula
the minimal detail that shows the arrangement of atoms in a molecule.
eg. CH3CH2CH2CH2OH
what is the displayed formula
the relative positioning of atoms and the bonds between them
define skeletal formula
the simplified organic formula shown by removing hydrogen atoms, leaving just carbon chains and alkyl chains, with the functional groups.
what is the general formula for alkyl groups?
CnH2n+1
what is the prefix of an alcohol?
hydroxyl-
what is the suffix of an alcohol?
-ol
what is the suffix of an aldehyde?
-al
what is the suffix of a carboxylic acid?
-oic acid
what are the prefixes of the first 4 haloalkanes?
fluoro-
chloro-
bromo-
iodo-
what is the suffix of ketones?
-one
define haloalkane
an alkane with a halogen attached to it
define structural isomer
compounds with the same molecular formulae but different structural formulae
what is the shape of an alkane molecule?
tetrahedral - 109.5 degrees
what kind of bonds are there in alkanes? define this term
sigma bonds - the overlap of orbitals between two atoms
in alkanes, what happens to boiling point as chain length increases? why?
as chain length increases boiling point increases - because there are more carbons - so more electrons - so stronger induced dipole-dipole interactions - more energy to break bonds.
in alkanes, what happens to boiling point after chains become very long?
boiling point levels off because the percentage increase of electrons become insignificant so the boiling doesn’t increase by that much.
how does a branched isomer effect the boiling point of an alkane?
branched isomers have lower boiling points - because straight chains have more surface contact - which means more induced dipole interactions.
branched isomers can’t get as close together so they have less interactions.
state the word equation for the complete combustion of an alkane
alkane + oxygen –> carbon dioxide + water
state the word equation for the incomplete combustion of an alkane
alkane + oxygen –> carbon monoxide + carbon dioxide + water
define heterolytic fission
the breaking of a covalent bond in which one of the bonded elements receives all of the bond pair electrons, resulting in a positive an negative ion
define homolytic fission
the breaking of a covalent bond in which each of the previously bonded atoms are given one electron each, resulting in two radicals
define a radical
a species with an unpaired electron (that is highly reactive)
what are the 3 steps of homolytic free radical substitution? describe them in terms of radicals present
initiation - in which 2 free radicals are formed
propagation - no. of radical doesn’t change. the reaction continues due to the continuous formation of radicals
termination - free radicals are consumed and react together
example of homolytic free radical substitution:
making chloromethane from methane and chlorine.
- what is the balanced symbol equation?
CH₄ + Cl➝ HCl + CHCl
example of homolytic free radical substitution:
making chloromethane from methane and chlorine.
- what happens in the initiation step? what is needed for this step? give the equation for it
initiation: UV light is needed to break the chlorine bond to create two chlorine radicals.
Cl₂ ➝ Cl• + Cl•
example of homolytic free radical substitution:
making chloromethane from methane and chlorine.
- what happens in the propagation step? give the equations for it
propagation: radicals are used then regenerated, creating a chain reaction.
Cl• + CH₄ ➝ CH₃• + HCl
Cl₂ + CH₃• ➝ CH₃Cl + Cl•
example of homolytic free radical substitution:
making chloromethane from methane and chlorine.
- what happens in the termination step? write 3 equations of how the reaction could come to this
termination: reaction stops because the radicals react together, removing themselves
Cl• + Cl• ➝ Cl₂
Cl• + CH₃• ➝ CH₃Cl
CH₃• + CH₃• ➝ C₂H₆
what shape do alkenes have? what bond angle? why?
trigonal planar - 120 degrees
because the sigma and pi bonds repel by equal amounts so create angles of 120 degrees (I think..?)
define sigma bond
overlap of orbitals between 2 atoms
define pi bond
overlap of p-orbitals above and below atoms -creates double bond in alkenes
what is an addition reaction?
when something is added to a species, creating only ONE product
alkene + hydrogen =? what is needed for the reaction?
alkane - nickel catalyst
alkene + water =? what is needed for the reaction?
alcohol - water must be steam and a phosphoric acid catalyst
define electrophile
something that accepts electrons
outline the three main steps of electrophilic addition of alkenes
- C=C electrons are accepted by electrophile and one bond is created
- a carbocation is formed and the lone electrons from the left over electrophile attract to it (intermediate)
- saturated substance is formed.
electrophilic addition: what three typed of carbocations can be formed? which is more stable?
primary: carbocation only bonded to ONE other carbon
secondary: carbocation bonded to TWO other carbons
tertiary: carbocation bonded to THREE other carbons
TERTIARY is more stable
electrophilic addition: how is the major product decided?
the most stable = the major product
define stereoisomerism
compounds with the same structural formula but different arrangement in space
what must an alkene have for there to be stereoisomerism?
each carbon in the C=C must have two distinct groups bonded EACH
if one carbon has two of the same group, there is no stereoisomerism
why can alkenes have stereoisomerism?
because the double bond restricts rotation
name two methods of identifying stereoisomers
cis-trans
E-Z
when would you use cis-trans methods?
when each of the two groups in question that are bonded to each carbon are the same
what would a cis alkene look like?
two groups on the SAME side of the C=C
what would a trans alkene look like?
two groups on OPPOSITE sides of the C=C
how do you decide whether an alkene is E or Z?
split the alkene in half
decide which is the high priority group
see whether they are on the same side or opposite sides.
what is considered a high priority group?
groups with the highest Mr
what would an E alkene look like?
two highest priority groups are on opposite sides
E for Enemies
what would a Z alkene look like?
two highest priority groups on the same side
Z for Zee Zame Zide
define polymerisation
monomers reacting together to make a polymer - repeated chain
how are monomers and polymers drawn in a polymerisation equation?
both with brackets with an ‘n’ outside representing number of units
polymer has extra bonds continued out the brackets
why can’t addition polymers be broken down in the environment?
because they are:
- saturated
- very stable
so bonds aren’t broken easily
suggest 6 ways of disposing of polymers
organic feedstock biodegradable combustion landfill photodegradable recycling
name 2 positives and 1 negative of using combustion to dispose of polymers
positives:
- produces heat which can generate electricity
- greenhouse gases (below) can be avoided using alkali scrubbers
negative:
1. CO2 is produced = greenhouse gas, and HCl gas is produced from burning Cl based compounds
how do you make a polymer biodegradable?
mixing plant based polymers with regular polymers to help them break down in the earth
what is photodegradable?
something that can be broken down by light
bonds are weakened by the absorption of light
how do you make a polymer photodegradable?
mixing photodegradable substances into the regular polymers
what is one problem with photodegradable polymers?
photodegradable polymers in landfill may not receive enough sunlight if they are buried in rubbish = not break down
