Organic Chemistry Study of the compounds of Carbon

Organic Chemistry: Study of the compounds of Carbon 7 million examples Inorganic Chemistry: Study of molecules without Carbon ( 1. 5 million examples)

Hydrocarbons • Organic molecules consisting only of carbon and hydrogen with covalent bonds. • Major components of fossil fuels such as coal, oil or gas. They consists of partially decomposed remains of organisms that lived millions of years ago. • Methane is a fossil fuel, it is easily made in anaerobic conditions with manure and bacteria (also in swamps or dumps)

Hydrocarbons CH 4 Methane

Methane Production Methane can be produced in: § Coalmines § Slurry pits § Waste dumps § Digestive tracts of animals

Hazards of Methane Production • Fires and explosions • Death by suffocation • Contributes to the greenhouse effect

Empirical Formula = formula represents the lowest ratios of the element in a compound Molecular Formula = a molecular formula describes the numbers of different kinds of atoms in a molecule Structural Formula = a structural formula represents a two-dimensional model of how the atoms are bonded to each other. Each dash represents a bonding pair of electrons. Condensed Structural Formula = structural formula written not drawn

**Ignore that it’s Spanish (I think)

Draw a carbon atom • How many monovalent atoms can bond to carbon? • What shape and bond angle will carbon molecule have? 109. 5 • What type of bond? Covalent or ionic

Definition • Saturated = chemical compound that has a chain of carbon atoms linked together by single bonds and has atoms filling all of the other bonding orbitals of the carbon atoms. (SINGLE BONDS ONLY- BONDING ORBITALS FULL) • Unsaturated compound is a chemical compound that contains carbon-carbon double bonds or triple bonds, such as those found in alkenes or alkynes, respectively. (CONTAINS DOUBLE/ TRIPLE BOND)

• Tetrahedral compounds are saturated – Alkanes – Chloroalkanes [Haloalkanes] – Alcohols • Where-ever there is a double or triple bond they become planar 11

Carbon skeletons can vary in length.

Organic compounds An aromatic compound is a compound that contain a benzene ring. Aliphatic compound is an organic compound that consists of open chains of carbon atoms and closed chains compounds (ring) that resemble them in chemical properties eg. Cyclohexane

Cycloalkanes are alkanes (only carbon to carbon single bonds) which form a ring structure. eg cyclohexane • The "straight" chain has carbon atoms that are able to rotate freely around their single bonds, sometimes linking up in a closed ring. • Ring compounds of the first four cycloalkanes =

Aromatic Hydrocarbons • Contain benzene rings Delocalised electrons Benzene: C 6 H 6 • unreactive (less than expected), • alternating double and single bonds with bond length between single and double bond length • Stable • insoluble in water • Toxic • Carcinogenic • good organic solvent • planar

Range and scope of aromatic chemistry • • Methyl benzene is used as a industrial solvent Pharmaceutical compounds, e. g. Morphine • Herbicides, e. g. Diuron • Detergents, e. g. Sodium dodecylbenzenesulfonate • • Dyes, e. g. Martius Yellow The acid-base indicators phenolphthalein and methyl orange are also aromatic compounds: Phenolphthalein, Methyl orange Benzene is carcinogenic •

Homologous series • Alkanes occur in what is called a homologous series. • A series of compound of uniform chemical type • Showing gradations in physical properties • Having a general formula for its members • Each member having a similar method of preparation • Each successive compound differs from the one before it only by a CH 2

Homologous series

Alkanes • Only have single bonds between carbons (saturated) • Have maximum amount of Hydrogens • End with –ane Ethane • Cn. H 2 n+2 • Fairly unreactive but do burn in oxygen, used as fuel due to high heat of combustion, cheap and clean products • Tetrahedral shape (not planar) 109. 5 o angles • Non-polar so immiscible in water C 1 -C 4 (gas) C 5 -C 12 (liquids) C 13 -C 31 (waxy solids) C 32+ (solids). Butane

C 1 to C 4 Gases C 5 to C 16 Liquids C 17 + Waxy Solids

Natural gas is pure methane Bottles gas is propane and butane

General formula Cn. H 2 n+2 Identify the number of H’s in each alkane • C 5 Hx • C 10 Hx • C 16 Hx • C 55 Hx • C 3 Hx • C 28 Hx • C 21 Hx • C 4 Hx • C 15 Hx What state? • • •

Need to know how to draw structural formula • Must know how to draw from nameor vice versa • CH 3 CH 2 CH(CH 3)CH 3

Branching • Skeletons may be branched or unbranched. Butane C 4 H 10 2 -methylpropane (commonly called isobutane)

Structural Isomers • Are compounds with same 2 molecular formula but different structural formulas • The number of isomers increases tremendously as carbon skeletons increase in size. • Only need to know to C 5 Structural Isomers of Butane

Naming alkanes (IUPAC) 1. Identify the longest continuous chain of carbons. = parent name/compound 1. The locations or other groups of atoms attached to the longest chain are identified and numbered by counting from the end of the molecule which keeps the numbering system as low as possible. 2. Hydrocarbon groups that are attached to the longest continuous chain and named using the parent name and changing the –ane suffix to –yl. 3. For groups attached, priority is given based on alphabetical order i. e. ethly before methyl

Functional groups • Is an atom or group of atoms which is responsible for the characteristic properties of a series of organic compounds • Eg. methyl, propyl • Eg. halogens • Electronegative functional groups increase the molecules reactivity with polar molecules and solubility in polar molecule eg. water

Chloroalkanes • Physical state: Liquid, except for chloromethane and chloroethane, which are gases at room temperature • Boiling points higher than the corresponding alkanes(most liquids except C 1 &C 2), due to polar C-Cl bond(s) (but only weak) • Not soluble in water • Soluble in non-polar solvents such as cyclohexane • Because of their weak polarity, they are useful organic solvents, e. g. for 1. removing grease and oil from machinery 2. removing oil etc. from clothes - dry cleaning • Fully halogenated alkanes are flame retardant so used in fire extinguishers

Naming chloroalkanes Last part of name comes from base alkane on which the molecule is built, e. g. chloroethane [2 carbons] l Number of chlorine atoms indicated by prefix mono, di, tri, tetra etc. in front of chloromethane, e. g. trichloromethane l Position of each chlorine atom given by a number before the name, e. g. 1, 2, 2 -trichloropropane l

Alkenes are different to alkanes; they contain DOUBLE COVALENT bonds. • Cn. H 2 n • Unsaturated • Ethene is the 1 st member Ethene • C 2 to C 4 are gases, boiling pt increases with increasing carbon chain • More reactive than alkane • • Test Undergoes addition for alkenes = 1. theyrxns turn bromine water colourless 2. acidified KMn. O 4 colourless. • planar Butene

Ethene is used to make polyethene By polymerisation rxn (addition rxn with H 2 as a by product) • Ethene is the gas that ripens fruit, and a ripe fruit emits the gas, which will act on unripe fruit. Thus, a ripe tomato placed in a sealed bag with green tomatoes will help ripen them. • Ethene is used to make ethanol for industrial use

Naming Alkenes – Naming is similar to naming alkanes except: • The longest continuous chain must contain the double bond. • The base name now ends in –ene. • The carbons are numbered so as to keep the number for the double bond as low as possible. • Number the double bond on parent (in word or before) i. e. pro-1 -ene, 1 propene • The number which identifies the location of the double bond takes priority to functional groups

Alkynes – An alkyne is a hydrocarbon with at least one carbon to carbon triple bond. – Naming an alkyne is similar to the alkenes, except the base name ends in –yne. – Even more reactive due to triple bond – Planar – Highly unsaturated – Cn. Hn-2

Alcohols In the alcohols it is the OH [hydroxyl] group General Formula Cn. H 2 n+1 OH Members of this Homologous Series are • • Methanol Ethanol Propanol Butanol CH 3 OH C 2 H 5 OH C 3 H 7 OH C 4 H 9 OH etc.

Classification

Primary Alcohols H H H | | | H - C - C - OH | | | H H H Propan-1 -ol The C to which the OH is attached has only got one C attached directly to it.

Secondary Alcohols H H H | | | H-C -C -C-H | | | H OH H Propan-2 -ol The C to which the OH is attached has got two C’s attached directly to it.

Intermolecular Force between molecules dictate it’s B. Pt. and M. Pt

Boiling Points of alcohols • Higher than expected for their RMMs • due to polar OH group • Polarity due to a difference in electronegativity between O and H • O = 3. 5 : H = 2. 1 difference 1. 4 • leads to Hydrogen Bonding • Compare Methanol and Methane [RMM approx 30]

Solubility is controlled by the molecules attraction to water • As a general rule ‘Like dissolves like’ i. e. polar substance will dissolve other polar substances. • The lines get a bit blurry when you have slightly polar substances as the can have slight solubility or poor solubility i. e. they dissolve little bit

Solubility Methanol in • (i) cyclohexane – not soluble methanol is polar cyclohexane is not • (ii) water - completely soluble or miscible [infinitely soluble] because it is polar. • Like dissolves like • Polar dissolves polar • As alcohol gets bigger the polar part becomes less significant so it becomes less soluble in water and more soluble in cyclohexane

• Ethanol and water can’t be totally separated by distillation. • Constant Boiling Mixture of 95% alcohol • To dry ethanol totally the last of water must be removed by drying agent e. g. Ca. O • Pure alcohol is called absolute alcohol

Butan-1 -ol in –(i) cyclohexane is soluble –(ii) water pretty insoluble • The polar OH group is becoming less significant as the molecule gets bigger

Comparison with water • Both have polar OH [hydroxyl] groups • Alcohols have a non-polar part • Water has a higher boiling point than alcohol because it has more polarity • It has 2 polar OH groups therefore H bonding is even more pronounced

Aldehydes • -CHO • end in anal • Planar • Boiling points higher than the corresponding alkanes, due to polar +C = O - group, but lower than the corresponding alcohols • Short chain aldehydes are soluble in water due to the polar carbonyl group • As the number of carbon atoms in a molecule of the aldehyde increases, solubility in water decreases, while solubility in cyclohexane increases Aromatic aldehyde Found in almond kernels

Ketone • End in -one • Physical state: Butanone and propanone are liquids at room temperature • Boiling points higher than the corresponding alkanes, due to polar +C = O - group, but lower than the corresponding alcohols • Short chain ketones such as propanone are soluble in water due to the polar carbonyl group • Ketones are soluble in non-polar solvents such as cyclohexane • Propanone is used as a solvent (e. g. In nail varnish remover)

Carboxylic acid • End in –oic acid • Physical state: Methanoic acid and ethanoic acid are liquids, while propanoic acid and butanoic acid are solids due to H bonding • Short chain carboxylic acids are soluble in water due to the polar COOH group • Carboxylic acids are soluble in non-polar solvents such as cyclohexane • Boiling points higher than the corresponding alcohols • This is because carboxylic acids form dimers, where two carboxylic acid molecules are held together by two hydrogen bonds • This is possible due to polarity in both the C=O and O-H bonds in each carboxylic acid molecule – Examples 1. 2. 3. 4. Methanoic acid is found in the sting of ants and nettles Ethanoic acid is the principal acid in vinegar Ethanoic acid is used in the manufacture of cellulose acetate Propanoic acid, benzoic acid and their salts (e. g. sodium benzoate)

COOH

Boiling or Melting Points • Ethanol = 78’ • Ethanoic Acid = 118’

Alcohol vs. Corresponding Carboxylic Acid B. Pt. Carboxylic Acids: have 2 H bonds between its molecules Alcohols: Have 1 Hydrogen bond between molecules

Dimer: a molecule or molecular complex consisting of two identical molecules linked together.

Solubility Of Carboxylic Acids

Esters are formed by the reaction of a carboxylic acid with an alcohol e. g. CH 3 COOH + Ethanoic acid CH 3 OH = Methanol CH 3 COOCH 3 + H 2 O Methyl ethanoate The first part of the ester name comes from the parent alcohol with the - anol changed to – yl and the second part of the name comes from the parent acid with the - oic acid changed to – oate.

Boiling Point and Solubility

• Physical state: Liquid • Boiling points higher than the corresponding alkanes, but lower than the corresponding alcohols • Soluble in water and non-polar solvents such as cyclohexane • As the number of carbon atoms in a molecule of the ester increases, solubility in water decreases, while solubility in cyclohexane increases • Occur naturally in fruits and flowers– are responsible for their pleasant smells and flavours • Fats and oils are naturally occurring esters of long chain carboxylic acids • Ethyl ethanoate is used as a solvent for printing inks and paints