Module 4: Core organic chemistry OCR A LEVEL CHEMISTRY

Aliphatic hydrocarbon

A hydrocarbon with carbon atoms joined together in straight or branched chains.

Alicylic hydrocarbon

A hydrocarbon with carbon atoms joined together in a ring structure.

Aromatic hydrocarbon

Contain at least one benzene ring or similar structural features.

Aldehyde

Carboxylic acid

Ketone

Aldehyde suffix

-al

Carboxylic acid suffix

-oic acid

Ketone suffix

-one

Alkane general formula

CnH2n+2

Alkene general formula

CnH2n

Alcohol general formula

CnH2n+1OH

Displayed formula

A formula showing the relative positioning of all the atoms in a molecule and the bonds between them.

Structural formula

a formula that shows the arrangement of atoms in the molecule of a compound.

Empirical formula

shows the simplest whole-number ratio of atoms of each element in the compound

Molecular formula

shows the types and numbers of atoms combined in a single molecule of a molecular compound

Skeletal Formula

A simplified organic formula, with hydrogen atoms removed from alkyl chains, leaving just a carbon skeleton and associated functional groups.

Unsaturated hydrocarbon

A hydrocarbon in which one or more of the bonds between carbon atoms is double or triple

Structural isomers

Compounds with the same molecular formula but different structural formula

How are structural isomers formed?(3)

-The alkyl groups change places.
-The functional group can be bonded to different parts of the parent chain.
-The functional group could be different.

Stereoisomerism

Compounds with the same structural and molecular formula but a different arrangement of atoms in space

E/Z isomerism

A type of stereoisomerism in which different groups attached to each carbon of a C=C double bond may be arranged differently in space because of the restricted rotation of the C=C bond.

E isomer

the isomer with the high-priority groups on opposite sides of the double bond

Z isomer

the isomer with the high-priority groups on the same side of the double bond

Cis-trans isomers

A type of E/Z isomerism where two substituents on each carbon atom are the same.
E=trans
Z=cis

Fission

Covalent bonds break

Homolytic fission

The breaking of a covalent bond with one of the bonded electrons going to each atom, forming two radicals.

Radicals

species with one or more unpaired electrons, shown as dots.

Heterolytic fission

The breaking of a covalent bond with both of the bonded electrons going to one of the atoms, forming a cation and an anion

Covalent bond formation

2 radicals or oppositely charged ions collide

Carbocation

An organic ion in which a carbon atom has a positive charge

Bonding in alkanes

sigma bonds, each carbon atom has a tetrahedral shape with a bond angle of 109.5.

How does branching affect boiling point?

lowers it, as there are fewer surface area interactions between molecules so they cant fit as neatly and increase the number of dipole-dipole interactions.

How does the carbon-chain length of alkanes affect the boiling point?

As the carbon chain gets longer the boiling point increase. As the chain gets longer the relative molecular mass increases, larger molecules have more surface area contacts which increases dipole-dipole forces, so more energy is need to overcome the intermolecular attraction.

Explain the reactivity of alkanes

They have a low reactivity due to high bond enthalpies and the sigma bongs have low polarity.

Combustion

A rapid reaction between oxygen and fuel that results in fire

Complete combustion

A combustion reaction in which the only products are carbon dioxide and water

Complete combustion equation

hydrocarbon + oxygen = carbon dioxide + water

Incomplete combustion

When a fuel burns in insufficient oxygen, producing carbon monoxide as a toxic product.

Incomplete combustion equation

hydrocarbon + oxygen -> carbon + carbon monoxide + water

Radical substitution

A type of substitution reaction in which a radical replaces a different atom or group of atoms.

What conditions are needed for radical subsititution?

UV light

What are the 3 steps of radical substitution?

Initiation
Propagation
Termination

Initiation

Formation of radicals

Propagation

The two repeated steps in radical substitution that build up the products in a chain reaction.

Termination

two radicals collide and make a stable product.

Shapes of Alkenes

trigonal planar with a bond angle of 120 degrees

Explain the reactivity of alkenes

More reactive than alkanes due to the C=C bond

Electrophilic addition

A type of addition reaction in which an electrophile is attracted to an electron-rich centre or atom, where it accepts a pair of electrons to form a new covalent bond.

Hydrogenation

Addition reaction in which hydrogen is added across a C=C bond, at a temperature of 150 degrees and a catalyst such as Nickel. An alkane is produced

Halogenation

addition reaction where a halogen is added across the C=C bond. The alkene becomes saturated and a dihaloalkane is produced. This can be used as a test for saturation.

Hydration

Addition reaction between a gaseous alkene and steam, it is used to make alcohols, the conditions involve high temperatures and pressures with a phosphoric acid catalyst.

Addition of Hydrogen Halides

Hydrogen halides are added across a C=C bond,under no specific conditions and form a haloalkene

Markownikoff's rule

a generalisation stating that the major product formed by the addition of an unsymmetrical reagent such as H-Cl, H-Br, or H-OH is the one obtained when the H atom of the reagent adds to the carbon atom of the multiple bond that already has the greater number of hydrogen atoms attached to it

Monomer

A simple compound whose molecules can join together to form polymers

Polymer

A long molecule consisting of many similar or identical monomers linked together.

Name 5 ways plastics are disposed of

-landfill
-combustion
-reusing
-recycling
-using them as organic feedstock

How do landfills work?

Large holes are dug into the landscape which are lined to stop contaminants and the rubbish is buried.

Disposing plastics by combustion

The plastics are burnt and the gases are removed by gas scrubbers where a base such as C.aO neutralises the acidic gas

How does recycling work?

The plastics are cleaned and melted down and reshaped into new products.

Organic feedstock

something organic (wood fiber, paper, cotton, etc.) that mold can use as an energy source.

Biodegradable polymers

Polymers can be manufactured to break down by microbes and the environment.
However this uses plant materials (which could be used for food)

Photodegradable polymers

Contain bonds that are weakened by absorbing light to start the degradation

Homologous series

A series of organic compounds with the same functional group but with each successive member differing by CH2

Functional group

group of atoms within a molecule that interacts in predictable ways with other molecules

Saturated

single carbon-carbon bonds only

What does a curly arrow represent?

Movement of an electron pair

Electrophile

An electron pair acceptor

Boiling point of alcohols

-contain a strongly electronegative O in the OH
-*hydrogen bonding*
-have higher boiling points than alkanes and ethers of similar mass

Solubility of alcohols

As the size of chain increases, solubility decreases because more energy is required to overcome hydrogen bond. Smaller relative to rest of molecule

Primary Alcohol

the -OH of alcohol is attached to an end carbon

Secondary Alcohol

An alcohol in which the hydroxyl (-OH) group is attached a carbon that is attached to two other carbons.

Tertiary alcohol

An alcohol in which the hydroxyl (-OH) group is attached to a carbon that is in turn attached to three other carbons.

Combustion of alcohols

Alcohols undergo combustion with O2 to produce CO2 and H2O.
CH3—CH2—OH + 3O2 --> 2CO2 + 3H2O + Energy

Oxidation of primary alcohols

Aldehyde -(Alcohol in excess + product distilled off immediately)
Carboxylic acid- (oxidising agent in excess + Under reflux )
also produces water
uses acidified potassium dichromate

Oxidation of secondary alcohols

~ Produce a ketone
~ Done under reflux
~ Ketones don't easily oxidise so final product
uses acidified potassium dichromate

Oxidation of tertiary alcohols

-tertiary alcohols cannot be oxidized b/c they are already as oxidized as they can be w/o breaking the C-C bond
-there is no H attached to the Carbon with the OH group so it doesn't have spare H to give up
-Alcohol oxidation involves removal of H so that the carbon can instead make another bond to O

Esterification of alcohols

-carboxylic acid+ alcohol=ester and water
-sulfuric acid catalyst

Naming esters

First part - alcohol
Second part - acid
suffix- oate

Dehydration

-alcohol heated with a strong acid
-product= alkene
-reflux with phosphoric or sulfuric acid

Halide substitution

-Halide takes the place of alcohol group to form a haloalkane
-acid catalyst

Nucleophile

An electron pair donor

Hydrolysis using aqueous alkali

-nucleophilic substitution
-heated under reflux with aqueous solution to form an alcohol

Chlorofluorocarbons

group of chemical compounds used in refrigerators, air conditioners, foam packaging, and aerosol sprays that may enter the atmosphere and destroy ozone

CFCs in the atmosphere

Cause ozone to be broken down

Chlorine radicals from CFCs

Nitrogen monoxide can decompose the ozone

Infrared radiation causes

covalent bonds to vibrate more and absorb energy

What does an infrared spectrum show

Absorptions of different bonds

Uses of an infrared spectrum

-monitor gases causing air pollution
-modern breathalyses to measure ethanol in breath

Mass Spectroscopy

Gives the MW and (in high resolution) the molecular formula by % abundance. The molecules of a sample are bombarded with electrons, causing them to break apart and ionize. These ions are accelerated through a magnetic field and the resulting force deflects the ions around a curved path.
-> Radius of curvature of their path depends on the "mass to charge ratio" (m/z) of the ion.
Most ions have a +1 charge. The magnetic field strength is altered to allow the passage of different sized ions through the flight tube and a computer records the amount of ions passing through at a given strength.

Base peak: largest peak
"Parent peak": peak made by the molecular ions (original molecules that did not fragment, missing one electron -> +1) should be on the right side of the spectrum with heavy isotopes.