Core Organic Chemistry

homologous series

the same functional group with successive members only differing by CH2

naming compounds functional groups: highest to lowest priority

carboxylic acid, aldehyde, ketone, alcohol, alkene, alkyl, haloalkane

carboxylic acid formula and suffix

-COOH (double bond oxygen to carbon), oic acid

aldehyde formula and suffix

-CHO (double bond oxygen to carbon), al

ketone formula and suffix

C-CO-C (double bond oxygen to middle carbon), one

alcohol formula, suffix and prefix

-OH, ol, hydroxy

general formula definition

a formula that represents a homologous series of compounds using letters and numbers

structural formula definition

a formula which shows the arrangement of atoms in the molecule of a compound but does not show all the bonds between them

displayed formula definition

a type of structural isomer that shows all the bonds between every atom in the compound

empirical formula definition

the simplest whole number ratio of the elements present in one molecule or formula unit of the compound

molecular formula

a formula that gives the exact number of atoms of each element present in the formula of the compound

skeletal formula

a diagram representation of an organic compound in which lines represent bonds between atoms and atoms are represented by their symbol

structural isomers

compounds that have the same molecular formula but different structural formula

E/Z stereoisomerism

the organic molecule must have a C=C and both carbons must be attached to different groups

what does the C=C bond prevent

will not allow the atoms to rotate freely

in stereoisomerism what does E stand for

entegen = opposite sides

in stereoisomerism what does Z stand for

zusammen = same sides

stereoisomerism definition

the same structural formula but with a different arrangement of atoms in a 3D spatial arrangement

Cahn-Ingold-Prelog (CIP) steps

locate the C=C bond and redraw it to show the subunits, focus on one carbon and assign priority to each substituent based on its relative atomic mass (highest atomic mass = highest priority), highest priority on same side = Z isomer, highest priority on different sides = E isomer

cis/trans isomers

isomers where one substituent group of each carbon on the C=C bond is the same

cis isomer

same side

trans isomer

different side

covalent bond definition

electrostatic attraction between a shared pair of electrons and nuclei of the bonded atoms

undergoing fission

during the first stage of a chemical reaction, activation energy affects the covalent bonds by causing them to break

curly arrows definition

model the flow of electron pairs during reaction mechanisms

where should a curly arrow start and finish

start from a bond, lone pair or a negative charge and finish on the atom they are moving to

dipoles

created when one element has a higher electronegativity than another in a bond

non-polar covalent bond

bonding electrons shared equally between two atoms - no charge on atoms

polar covalent bond

bonding electrons shared unequally between two atoms - partial charge on atoms

homolytic fission

occurs when a covalent bond breaks and each electron goes to a different bonded atom

what does homolytic fission generate

generates two highly reactive, neutral species (radicals)

heterolytic fission

occurs when a covalent bond breaks and both electrons go to one of the bonded atoms

what does heterolytic fission form

forms a cation and an anion

how is a covalent bond formed

two radicals or two oppositely charged ions collide

why do alkanes have a low reactivity

due to high bond enthalpies (large activation energy) and carbon-hydrogen bonds with low polarity

condition of reaction for alkanes

presence of ultraviolet radiation

overall reaction of alkane

a hydrogen atom in an alkane is substituted by a halogen atom

free radical definition

any species with a free, unpaired electron

reactions involving free radicals…

can often be explosive and difficult to control due to the extremely reactive nature of the radicals

what are the three free radical substitution steps

initiation, propagation, termination

initiation

the formation of radicals

propagation

two repeated steps that build up the desired product in a side reaction (always the same number of radical species)

propagation: step 1

an alkyl radical and any halogen are made

propagation: step 2

the desired product and and a radical are made

termination

two radicals covalently bond and make a stable products

3 steps of the mechanism can occur at the same time which may result in

substitutions of halogens in different positions, multiple substitutions of halogens on an alkane

when bonds are formed in alkanes…

energy is released and the system becomes more stable

‘promotion’ in alkanes

there is a small gap between 2s and 2p orbitals, so it pays the carbon to provide a small amount of energy to promote an electron from 2s to the empty 2p

hybridisation process

a process where electrons rearrange themselves

how is a C-C sigma bond formed in alkanes

two sp3 orbitals in neighboring carbon atoms overlap

how is a C-H sigma bond formed in alkanes

remaining three sp3 orbitals on each carbon overlap with 1s orbitals from three separate hydrogen atoms

in alkane structure shape

each carbon atom has a tetrahedral shape and bond angle of 109.5

properties of alkanes

non-polar, without any significant dipoles

why are alkanes non-polar and without any significant dipoles

as the carbon and hydrogen Pauling electronegativity values are similar

what causes an instantaneous dipole

an occasional lack of balance in charge distributions due to electrons moving round the shells all the time

induced dipole definition

dipole forces between alkanes

how do instantaneous dipoles affect neighboring molecules

will induce dipoles in them

what is London force

weakest intermolecular force of attraction (induced dipole-dipole interaction)

when alkane state changes

pairs of molecules stay together, covalent bonds do not break, weak intermolecular forces (between pairs of molecules)

carbon-chain length

as an alkane chain gets longer, its relative molecular mass increases. Larger molecules have more surface area contacts between adjacent molecules. This increases the number of induced dipole-dipole forces. So more energy is needed to overcome the intermolecular attraction in order that the alkane can change shape.

structural isomers + boiling points

structural isomers of alkanes have different boiling points

why do structural isomers have different boiling points

the more branched the compound is the fewer surface interactions there are between molecules due to the molecules not being able to fit together as neatly so fewer london dispersion forces

induced dipole-dipole attractions in branched alkanes

branched molecules have fewer induced dipole-dipole attractions compared to the straight-chain isomer with the same molecular formula, leads to branched molecules having a lower boiling point

alkanes in combustion

alkanes can transfer their stored energy chemical energy to a usable form

complete combustion

oxidising a fuel in a plentiful supply of air

incomplete combustion

oxidising a fuel in a limited supply of air

complete combustion equation

hydrocarbon + O2 → CO2 + H2O

incomplete combustion potential products

carbon monoxide, carbon dioxide, water, soot (carbon)

what are C-H bonds in alkenes

sigma bonds

C-C sigma bond in alkenes

formed between two carbon atoms using the direct overlap of the electron clouds of the two atoms

Pi bond in alkenes

formed by the electrons in the adjacent P orbitals overlapping above and below, this can only be made after a sigma bond has been formed

How does the Pi bind restrict rotations

it holds the atoms in position by restricting rotation around the double bond

how does restricting rotation affect the shape of alkenes

alkene molecules have a flat shape in the region of the double bond

why is the pi bond reactive

the pi bond is the reactive part of the molecule because of the high electron density around it

how is the alkene shape formed

the covalent bonds between the two carbon atoms, each of these electron densities repel by the same amount front bond angles of 120 which results in a trigonal planar shape

alkenes physical properties: boiling point

increases with molecular mass/size due to increased dipole-dipole interactions, decreases with isomers with more branching, lower members of series are gases at RTP

alkenes physical properties: solubility

non-polar so insoluble in water but soluble in organic solvents

electrophiles definition

electron pair acceptors

what are electrophiles attracted to

electron rich C=C

why do pi bonds break more regularly or easily

due to low enthalpy

why do double bonds attract electrophiles

double bond is an area of high electron density

primary carbocation

one carbon chain attached to C+

secondary carbocation

two carbon chains attached to C+

tertiary carbocation

three carbon chains attached to C+

most to least stable carbocation

tertiary, secondary, primary

monomer definition

small molecules that are used to make polymers

polymer definition

macromolecule made from small repeating units/monomer

bonds during addition polymerisation

monomers have their pi bond broken, the electrons from each pi bond make a sigma bond with a neighbouring carbon atom on another monomer - this connects into a long saturated carbon chain

ways to dispose of polymers

landfill, combustion, reusing, recycling, feedstock, biodegradable, photodegradable

disposal of polymers: combustion

released CO2, adds to global warming, depending on polymer can produce HCL, scrubbers (CaO) used to neutralise acidic gas, loads of energy released for generating electricity

current disposal of polymers: feedstock

a chemical used to support a large-scale chemical reaction, create small organic molecules from recycling, used to create new plastics or other reactions

problems with waste polymers

additional polymers are incredibly stable, finite resource

uses of ethene

plastic bags and bottles