Organic Chemistry

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Hydrocarbon - a compound consisting of only hydrogen and carbon

Carbon-carbon bond can be single, double or triple.

The bonds are always non-polar

Alkanes are hydrocarbons with only single bonds

homologous series

successive compounds differ by a CH2

Compounds that have the same molecular formula but different structures are called isomers

Alkenes are hydrocarbons with at least 1 double carbon-carbon bond

homologous series

-ane suffix changes to -ene

unsaturated with regard to hydrogen (does not have max. number possible)

Alkynes are hydrocarbons with at least one triple carbon-carbon bond

homologous series

-ane suffix changes to -yne

Naming Alkanes

Identify the longest continuous chain = parent name, goes at the end

Identify the locations of other groups of atoms attached to the longest chain.

Number these by counting from the end of the molecule closest to the group (to keep the number low)

Name these using the parent name of the group and changing the -ane suffix to -yl

Use the prefixes 2: di, 3: tri, 4: tetra, 5: penta if there are more than one of a group

Naming Alkenes

Similar to Alkanes, but:

The longest continuous chain must contain the double bond

Carbons are numbered to keep the number for the double bond as low as possible

Base name is given to a number which identifies the location of the double bond

Naming Alkynes

-yne suffix used, rather than -ane or -ene

Cycloalkanes

Alkanes which form a ring structure

Halo-alkanes

An alkane with one of the following halogens, found after the alkyl group when naming

Fleuro-

Chloro-

Bromo-

Iodo-

Aromatic Compound

Based on the benzene ring

Benzene Ring

C6H6 - the bonds are between single and double, giving it chemical properties different to double-bonded compounds.

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Polarity

Molecule Shape

Lewis structure provides a 2D model

Shape is described by the geometric figure formed when atomic nuclei are imagined to join in straight lines

VSEPR - Valence Shell Electron Pair Repulsion

pairs of valence shell electrons are arranged as far apart from each other as possible

results in geometrics that minimise the energy of the molecule

Linear - 2 lone pairs of electrons

Trigonal Planar - 1 central atom surrounded by 3 other atoms, no lone electron pairs

Trigonal Pyramidal - 1 lone electron pair, 4 electron domains (3 bonds + lone pair)

Tetrahedral - 1 central atom surrounded by 4 other atoms, no lone electron pairs

Bent/V-shaped - 1 or 2 lone electron pairs, 3 or 4 electron domains (2 bonds + 1 or 2 lone pairs)

Moving down the group, atoms from longer bonds

Multiple bonds are shorter stronger than single bonds

more electrons = greater attraction to positive nuclei

"electron glue" between the two nuclei

Due to polarity of the bonds and how they are arranged around a central atom, a molecule can be polar or non-polar

Shape and bond polarity determine if a molecule if polar or non-polar

Dipole - a polar molecule, with a positive end and a negative end

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Secondary Forces - Intermolecular forces

Primary forces - intramolecular: covalent, ionic and metallic

(London) Dispersion/Van Der Waals Forces - non-polar molecules

Dipole-Dipole Forces - polar molecules

Hydrogen Bonding - polar molecules with O-H, N-H, F-H

1/10 the strength of primary bonds

Primary bonds represented by solid lines

Secondary bonds represented by dotted lines

To determine secondary bond type

polar bonds

molecule bonds

polarity of shapes

non-polar: tetrahedral, linear, trigonal planar

polar: bent, trigonal planar

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Functional Groups

an atom or group of atms present in a molecule that give rise to particular chemical properties of the molecule

Amines (amino acids) - NH2

Alkyl - alkane chain (carbon single bonded to hydrogen) that has lost a terminal hydrogen

Hydroxyl - OH group - alcohol: three categories

primary - one or zero hydrocarbon chains attached to carbon containing hydroxyl

secondary - two hydrocarbons chains attached to carbon containing hydroxyl

tertiary - three hydrocarbon chains attached to carbon containing hydroxyl

Carboxyl - COOH - one oxygen double bonded to the carbon and the other bonded to carbon and hydrogen with single bonds

Carbonyl - carbon double bonded to oxygen

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Organic Chemistry - the study of the chemistry of carbon compounds

An organic compound is a compound that has carbon as the principal element.

An inorganic compound is any compound that is not organic.

Carbon is unique

6 electrons in total, 4 in valence shell

room for 4 bonds to other atoms

Tetrahedral geometry around the carbon-carbon bond

chain of carbon atoms makes a zigzag pattern

usually simplified to look like a straight chain, but is still zigzag

3 types of chain

Straight chain

Branched chain

Ring chain

Saturated - All single bonds, cannot make any more bonds, maximum number of hydrogens

Unsaturated - At least one double bond, does not have maximum number of hydrogens

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Alcohols

An organic compound with a hydrogen replaced by a hydroxyl (OH) group.

Suffix -ol used when naming: eg methane becomes methanol

Hydroxyl group is polar

Short chain alcohols are soluble in both non-polar alkanes and water.

Two hydroxyl groups - diol (glycol)

Three hydroxyl groups - triol (glycerol)

Primary - 1 carbon bonded to the carbon with the hydroxyl group (OH on end of carbon chain)

Secondary - 2 carbons bonded to the carbon with the hydroxyl group (OH within carbon chain)

Tertiary - 3 carbons bonded to the carbon with the hydroxyl group (OH within carbon chain)

Petroleum

The mixture of alkanes, cycloalkanes and aromatic hydrocarbon.

Formed by slow decomposition of buried marine life, mainly plankton and algae.

During formation, petroleum is forced through porous rock until it reaches an impervious layer of rock.

Forms an accumulation of petroleum and saturates porous rock, creating an oil field.

Crude oil is petroleum pumped directly from the ground.

Complex mixture of hydrocarbons with one or two carbon atoms - limit of about 50 carbon atoms.

Must be separated by distillation.

Hydrocarbon derivatives are formed when one or more hydrogen atoms are replaced by an element or a group of elements other than hydrogen.

Halogens can add to a hydrocarbon, forming an alkyl halide.

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Ethers, Aldehydes and Ketones

An ether has a general formula ROR' (R = any length of carbon)

An aldehyde has a carbonyl group (Carbon double bonded to oxygen) attached to a terminal carbon atom.

Suffix -al

A ketone has a carbonyl group attached to an internal carbon atom.

Organic acids are acids derived from living organisms, from metabolism or as a defence mechanism.

Long chain organic acids are fatty acids.

Also called carboxylic acids, as they contain the carboxyl functional group (COOH)

Esters are condensation products of carboxylic acids, with the removal of water (dehydration synthesis)

Carboxylic Acid + Alcohol

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Organic Compounds of Life

Polymers - long chains of small units that are put together.

Macromolecule

A combination of many small similar molecules, polymerized into a chain structure.

There are three main types of macromolecules that control all activities and determine what an organism will do and become.

Proteins

Nucleic Acids

Carbohydrates

Cells are made up of macromolecules formed inside the cell. Other macromolecules control formation of these.

Metabolism is the breaking down or building up of macromolecules.

Breaking down releases energy - energy source

Building up requires energy, obtained from breaking down

Proteins are macromolecules that are polymers of amino acids.

Functionally, they are enzymes - they catalyze reactions to lower amount of energy required to build up macromolecules.

20 amino acids go into producing proteins.

Arrangement of amino acids in polymer determine structure of protein - determines function.

Carbohydrates are a large group of compounds generally called sugars, starches and cellulose - sugars or polymers of sugars.

Strong source of energy - cell respiration.

Glucose is the carbohydrate used most by animals.

monosaccharide - just one sugar unit - dissolves, to a point, in water

disaccharide - 2 sugar units - doesn't dissolve in water as chain is too long

polysaccharide - many sugar units - doesn't dissolve in water as chain is too long

Starch is a storage carbohydrate used by plants.

Glycogen is a storage carbohydrate used by animals.

Cellulose is a polysaccharide used in plant cell walls to maintain structure

Starch and cellulose are polymers of glucose - small difference in bonding arrangement

Fats and Oils

Humans take in amino acids and use them to synthesise proteins - 10 essential amino acids not synthesised by humans

Humans take in carbs and use breakdown as energy source.

When carbs are taken in greater quantities than required, leftover is converted into fats (animals) and oils (plants) as long term energy storage.

Animal fats are either saturated or unsaturated; mostly saturated, stored in adipose tissue as insulation, protection and later use.

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Application

Alkanes

Combustion - alkane + oxygen = carbon dioxide and water (complete combustion)

Substitution - halogens swap with Hydrogen atoms and substitute into alkane

Alkenes/alkynes

Combustion - need more oxygen to undergo complete combustion

Combustion - incomplete combustion results in black smoke or carbon dioxide as a waste fuel = pollution

Addition - halogens break double/triple bonds and bond to alkene/alkyne - moles of halogen=number of double/triple bonds

Alcohols

methods to distinguish between alcohol classes

primary alcohol + dichromate (orange) = chromate (green) + aldehyde

aldehyde + dichromate = carboxylic acid

carboxylic acid has 2 polar groups - stronger hydrogen bonds, strongest attraction between molecules, highest b.p.

carboxylic acid + carbonate = carbon dioxide (bubbles) + water + carboxylate ion

carboxylate ion more likely to dissolve in water - ion-dipole bonding - polar molecule

secondary alcohol + dichromate (orange) = chromate (green) + ketone

ketone will not react with dichromate as aldehyde does

tertiary alcohol + dichromate (orange) = no reaction

Esters