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Organic Compounds Organic Compounds Organic compounds are those compounds found in any organism that is living or was once living compounds from never living substances are referred to as “inorganic” Chemical Definition: Organic Compound – any compound that contains the element carbon -- The definition has also changed because organic compounds can now by synthesized in laboratories What it does not include •Carbon Monoxide •Carbonates •Hydrogencarbonates What else ? • Can contain –Hydrogen (Most do) –Oxygen (many do) –Nitrogen (some do) –Halogens (some do) Carbon’s Bonding Pattern • Carbon has 4 electrons in its outer shell. To satisfy the octet rule, it needs to share 4 other electrons. This means that each carbon atom forms 4 bonds. • The 4 bonds are in the form of a tetrahedron, a triangular pyramid. • Carbon can form long chains and rings, especially with hydrogens attached. • Compounds with just carbon and hydrogen are “hydrocarbons”: non-polar compounds like oils and waxes. Bonding in Organic Compounds • Usually covalent with single bonds being sigma (σ) type if all bonds are single the compound is said to ne saturated • Compounds with Double / triple bonds are said to be unsaturated and contain one sigma and the rest Pi (π) bonds Pi Bond Sigma Bond Bonding in Organic Compounds • Aromatic compounds with a benzene ring have a special mixed type of bonding (explained later) • Organic compounds with no benzene ring is said to be aliphatic Classification • Important when there are: • 7 million Organic Compounds • 1.5 million Inorganic Compounds Classification • Grouped into families called homologous series • Each series has a general formula and specific chemical properties Classification • After that we classify according to structure –Look at the central (key) Carbon atoms and depending on if they are tetrahedral or planer...we know things about the compound Tetrahedral Carbon Methane is Tetrahedral 0 109.5 H C H H H 4 equivalent C-H bonds (s-bonds) All purely single bonds are called s-bonds Methane is Tetrahedral 0 109.5 The shape is explained by the mutual repulsion theory In saturated organic compounds all of the carbon atoms are tetrahedral We will be looking at Alkanes Chloroalkanes Alcohols Physical Properties of Alkanes Non-polar molecules, which are less dense than water. Alkanes are immiscible with water making two layers. Van-der Waals or dipole-dipole attractive forces, and not H-bonding (as in polar molecules) are the main intermolecular forces Physical Properties of Alkanes Alkanes show regular increases in bpt and mpt as molecular weight increases down the homolgous series These weak intermolecular forces operate over small distances, arising because the electron distribution within molecules at any given instance is not uniform. Resulting in tiny electrical attractions between molecules. These temporary dipoles hold alkanes as liquids or solids, and must be overcome in order to vaporize a liquid or melt a solid (wax) Uses of Alkanes as fuels • Useful due to their high heat of combustion • Natural gas = mainly Methane • LPG = Propane and Butane • Petrol = Mixture of hydrocarbons (5 – 10 C alkanes) • Kerosene = 10 – 14 C alkanes used for heating fuel and Jet fuel Chloroalkanes • Alkane with one or more hydrogen atoms replaced by a chlorine atom – e.g. methane to chloromethane – Note that the central atom (C) is still tetrahedral • After the Hydrogen is replaced the remainder of the molecule is known as an alkyl group • In Methane CH3 is left (Methyl group) • Other Alkyl groups include –ethyl group • In ethane C2H5 is left –propyl group • In propane C3H7 is left –butyl group • In butane C4H9 is left • In other words they are named after the alkane they are derived from • Chloromethane Chloro........... indicates the presence of a Chlorine atom CH3Cl • > 1 chlorine atom and we need another prefix – Dichloromethane CH2Cl2 • More than 1 chlorine atom and we need another prefix No. Cl Name of Compound atoms Chemical Formula 1 Chloromethane CH3Cl 2 Dichloromethane CH2Cl2 3 Trichloromethane CHCl3 4 Tetrachloromethane CCl4 Structural Formula • More than 1 carbon and we need to: • Indicate the position of the chlorine atom on the chain • Name from the chlorine end with one exception* 2 •*Either end will be C=1 •But > 1 Cl atom and you must number 1 chloroethane • Example 15.1 (a) (write up for homework) • Name and draw the structural formula for CH2ClCH2Cl • Naming: CH2ClCH2Cl • 2 chlorines so it starts with di• One chlorine atom attached to each carbon so we need to number .....1,2 • Derived from the alkane ethane • Name= 1,2 dichloroethane • Example 15.1 (a) • Name and draw the structural formula for CH2ClCH2Cl Try this one on your own Example 15.1 (b) • CH3CCl3 3 chlorines so starts with tri- All 3 are on the same carbon so when we number they all receive the same number Derived from ethane Hence: 1,1,1 trichloroethane What if it’s a propane or a butane derivative • Same rules apply...see example 15.2 (a-e) CH2CHClCH3 1 chlorine so starts with just chloro on the 2nd carbon so when we number Derived from propane Hence: 2, chloropropane • What’s this: • CH2ClCH2CH3 • Or this • CH3CH2CH2Cl OR Why • 1 chlorine atom so we start at chloro • Attached to the first carbon so we number = 1 • Remember we number from the chlorine • Derived from propane (C3H8) • Hence: 1, chloropropane Another example • CH3CH2CHClCH3 • 1 chlorine attached at carbon 2 • Derived from butane (C4H10) • Hence: 2, chlorobutane Butane 2, chlorobutane Homework • Copy out Examples 15.2 a - e Physical State and Properties • Carbon – Chlorine bond is polar • Chloroalkanes are insoluble in H2O • Soluble in non polar solvents (cyclohexane & methylbenzene) • Higher BP than other alkanes (polar nature) • Higher BP is also found in longer chain molecules • Most are liquid except for Chloroethane and chloromethane (gases) BP of Chloroalkanes containing one chlorine atom increases as the carbon chain increases BP Carbons Physical State and Properties Chloroalkane BP(K) Chloromethane Chemical Formula CH3Cl Chloroethane CH3CH2Cl 285 1-Chloropropane CH3CH2CH2Cl 1-Chlorobutane 249 320 CH3CH2CH2CH2Cl 352 Chloroalkanes are used as solvents (dry cleaning) Alcohols • Homologous series with general formula CnH2n+1OH • All alcohols have an OH functional group • OH replaces an Hydrogen atom in the alkane • All the carbons are tetrahedral in shape • Named by replacing e of alkane with ol Alcohols • If there is more than 3 carbons we need to indicate where the OH (hydroxyl) group is • If its positioned at the end then this gets priority and is given the prefix 1 • The carbon attached to this OH grp will have no more than one carbon bonded to it (except in Methanol where it is bonded to 3 hydrogen atoms) Carbon attached t only 1 other carbon • These alcohols are called Primary Alcohols here are the first 4 Methanol Ethanol Propan – 1 - ol Butan – 1 - ol Homework • Draw table 15.3 Secondary Alcohols • Have 2 carbons attached to the carbon with the OH group............example Propan – 2 - ol Carbon attached to 2 other carbons Example 15.4 • Write the name and structural formula for the secondary alcohol containing four carbons • If its a secondary alcohol then the primary carbon cannot be at the end so..... Example 15.4 • As it has 4 carbons it does not matter which of the middle two contain the hydroxyl (OH) grp so we just name the carbon with this group “2” Example 15.4 • The name is decided by the alkane grp it is derived from (butane), the OH group makes it butanol and the position of the OH makes it butan – 2 - ol Physical State and Properties Alkane Formula BP (K) Alcohol Formula BP(K) Ethane C2H6 184 Methanol CH3OH 338 Propane C3H8 231 Ethanol C2H5OH 351 (gas @RT) (Liq @RT) Butane C4H10 272 Propan-1-ol C3H7OH 371 Pentane C5H12 309 Butan-1-ol 390 C4H9OH Because of hydrogen bonding and dipole-dipole interaction alcohols have different properties to Alkanes Boiling point (K) Alcohols Alkanes Alcohols have a much higher BP than alkanes even though they have a similar Mr Relative Molecular Mass An alcohol may be thought of as a compound very similar to a water molecule which has replaced an hydrogen atom with an alkyl group We refer to the alkyl group by the letter “R” σ- σ+ Polar OH group results in hydrogen bonding between molecules More electronegative O2 (-ive charge) attracts positively charged Hydrogen The hydrogen bonds strengthen the stability of the molecule and so it remains liquid at room temperature The hydrogen bonds need to be broken before it can become a gas and this takes more energy hence raising the BP Wines and beers are mixtures of ethanol and water They mix due to hydrogen bonding between Oh groups in each Solubility decreases as the hydrocarbon chain increases Occurrences and Uses Most ethanol is made by hydration of ethene + HOH water ethene Ethanol Fermentation of alcohol Ethanol in drinks like wine is made by fermentation of sugars in fruits Involves a series of biochemical reactions requiring enzymes found in yeast The enzymes break down the sugars to give ethanol and carbon dioxide Fermentation of alcohol C6H12O6 (aq) 2C2H5OH (aq) + CO2 (g) The process is anaerobic to avoid the oxidation of ethanol to ethanal and ethanoic acid Brewing Used to make beer – raw material malted grain End result is alcohol content of 3 – 5% v/v ethanol Whiskey is made from fermented malted barley which is ten distilled to concentrate the alcohol to about 40% v/v ethanol Fuel Fermentation of sugar cane makes ethanol and then mixed with petroleum products to make a motor fuel instead of petrol Solvent Ethanol is a very good solvent that evaporates easily Used in paints, glues, perfumes, aftershave Methylated spirts ...mostly ethanol with a little methanol and dye (poisonous) Planer Carbon Ethene C2H4 • Ethene is a planer molecule • Planer carbon atoms are a feature of many homologous series • C=C or C=O bonds demonstrate a planer atoms although other carbon atoms in the molecule may be tetrahedral • Double bonds mean the molecule is unsaturated We will be looking at Alkenes Aldehydes Ketones Carboxcylic acids Esters Aromatic compounds Alkenes • Homologous series of hydrocarbons (CnH2n.) • Unsaturated (C=C) • First three members are gases @ RT • Longer chains are liquids and solids • Increase in BP as the carbon chain increases • Ethene is the first member • Alkenes are Important industrial chemicals...especially ethene • Much more reactive than alkanes • Ethene C=C double bond can undergo addition reactions • Ethene (alkene) by addition of itself can become a very long chain alkane • More on addition reactions later Aldehydes • Homologous series of hydrocarbons (CnH2n+1CHO) where n = 0,1,2,3,etc... • All contain a carbonyl group C=O )polar covalent double bond) • In aldehydes there is always an Hydrogen atom bonded to the carbonyl group • In Methanal (HCHO) the carbon found in the carbonyl group is the only one in the molecule • The Carbonyl carbon is planer • The functional group of the aldehydes is CHO • Aldhydes are names by replacing the e at the end of the relevant Alkane with al • Molecular formula is found by replacing the last carbon in the chain from being part of a Methyl group to being part of a CHO group Example 15.5 • Write the name and structural formula of the aldehyde containing 2 carbons • Base alkane is ethane (CH3CH3) so the name of the aldehyde is ethanal • Molecular formula is found by replacing the last carbon in the chain from being part of a Methyl group to being part of a CHO group • So.......CH3CHO • Learn the first four aldehydes Name of Aldehyde Methanal Ethanal Propanal Butanal • Learn the first four aldehydes Chemical Formula HCHO CH3CHO CH3CH2CHO CH3CH2CH2CHO Methanal Ethanal propanal Butanal Physical State and Properties • Presence of C+O means the molecule is quite polar • Dipole – Dipole attractions between adjacent aldehyde molecules • Higher BP than relevant alkane • Lower BP than relevant Alcohol •Methanal is Gas at RT •Others are Liquids @ RT • Hydrogen bonding between aldehydes cannot occur • Hydrogen is only bonded to Carbon • Polarity of the C=O bonds mean that hydrogen bonding can occur between water and the CHO group • Smaller aldehydes dissolve in water • The longer the chain the lower the solubility • Soluble in non polar solvents like cyclohexane Occurrences and Uses • Found in nature –Glucose –Benzaldehyde....found in the kernel of almond nuts Ketones • Homologous series with formula R1COR2 • R 1 and 2 are usually Alkyl groups • All contain C=O (carbonyl Grp) as well, but unlike aldehydes this group is in the centre of the chain (no hydrogen bonded to the C=O grp) • Named by replacing the -e at the end of the relevant alkane with –one Alkyl Grp Replaces CH2 • With 2 x alkyl groups and 1 x carbonyl group there must be at least 3 carbons • Molecular formula is found when the central hydrogen atoms are replaced with a C=O Example 15.6 • Name the chemical formula and draw the structural formula of the ketone containing 3 carbons Example 15.6 • Corrosponding alkane is Propane so the ketone is Propanone and the formula is CH3COCH3 Name the first two ketones • Learn the molecular and structural formula Name of Ketone Propanone Butanone Physical State and properties • Similar properties to aldehydes • Lower Ketones are soluble in water • All are soluble in organic solvents • Higher BP than relevant alkane Occurrences and Uses • Many are found in nature • Testosterone & Progesterone....Human sex hormones • Butter, Ginger Oils and Spearmint,Nail varnish Remover Carboxylic Acids • Homologous series, formula CnH2n+1COOH (where n= 0,1,2,3,4,etc) • COOH is functional group • Structural formula is combination of a Carbonyl grp and an hydroxyl group but properties are distinctive Carboxylic Acids • Named by replacing the -e on the alkanee with –oic • Molecular formula found by replacing the last Methyl group with COOH Example 15.7 • Name and structural formula for carboxylic acid with 2 carbons • Name: • Alkane to carboxylic = ethane to ethanoic Example 15.7 • Chemical Formula –CH3COOH Learn the first four Name of Carboxylic Acid Methanaoic Ethanaoic Propanaoic Butanaoic • Learn the first four aldehydes Chemical Formula HCOOH CH3COOH CH3CH2COOH CH3CH2CH2COOH Homework • Draw the four structural formula Physical State and Properties • Lower Carboxylic acids are colourless with distinctive smell • BP higher than relevant alkane and alcohols • Higher BP due to formation of hydrogen bonding resulting in dimers (2 carboxylic acids held together by hydrogen bonds) Physical State and Properties Alkyl Grp or H Alkyl Grp or H Hydrogen bonded dimer • Hydrogen bonding also happens in water with lower carboxylic acids • Up to 4 carbon carboxylic acids are highly soluble in water but as the chain lengthens the solubility decreases Occurrences and Uses • Methanoic aacid is the iritating fluid used by ants and nettles • Countermeasure is Sodium hydrogencarbonate found in Bread soda (weak base) Occurrences and Uses • Ethanoic acid –Ethanol oxidises to ethanoic acid .....spoiling wine –Process used to make vinegar –Manufacture of cellulose acetate (varnish, lacquer, rayon) Occurrences and Uses • Propanoic acid • Benzoic acid • Sodium Benzoate (a salt of Benzoic acid) Used in food preservation Esters • Derived from Carboxylic acids (not alkanes) • Represented as R1COOR2 • Esters consist of 2 parts 1. An alkyl group derived from an alcohol 2. R1COO from carboxylic acid where “R” is either a hydrogen atom or a alkyl group Formula is R1COOR2 • Naming is based on the 2 parts • The alkyl group derived from the alcohol ...so methyl, ethyl, propyl etc..... • The carboxccylic acid ending in –oic which we replace –oate – Methanoic goes to methanoate • Full thing: Methyl Methanoate Example 15.8 • Name, Chemical and structural formula for ester derived from ethanoic acid (CH3COOH)and Methanol (CH3OH) • Methyl • Ethanoic • Methyl ethanoate Methyl ethanoate • Chemical Formula • We write the acid first and leave out the last Hydrogen so that we can add on the Alkyl group • Hence CH3COOH (carboxylic acid) is written CH3COO • The alkyl group (methyl, ethyl etc..) from the alcohol is added • Chemical Formula • And we end up with the following for methyl methanoate • CH3COOCH3 • Structural formula follows the same rules Ester linkage Methyl Methanoate Learn the esters containing four carbons Name of Ester Chemical Formula Methyl Methanoate HCOOH3 ethyl methanoate HCOOC2H5 propyl methanoate HCOOC3H7 Methyl ethanoate CH3HCOOCH3 ethyl ethanoate CH3HCOOC2H5 Methyl Propanoate C2H5COOCH3 Homework • Draw the structural formulas for the esters containing four carbons Physical State and properties • • • • • • Methyl Methanoate ethyl methanoate propyl methanoate Methyl ethanoate ethyl ethanoate Methyl Propanoate All of these are liquids C=O linkage is polar resulting in intermolecular forces but no actual hydrogen bonding between adjacent esters BP is the same as relevant aldehyde and ketone Hydrogen bonding can happen in water due to polar C=O (only with esters 5 carbons and under) Soluble in non polar solvents Occurrence and Uses • Strong fruity smell • Many occur naturally – Fruit flavours (mango has 8 esters including ethyl ethanoate) • Artificial flavours in processed foods • ethyl ethanoate used in paints and inks • Fats and Oils are naturally occurring esters of long chain Carboxyillic acid Aromatic Compounds • Derived from fractional distillation of crude oil (benzene) and the Dehydrocyclisation of low octane hydrocarbons – (removal of hydrogen from straight chain hydrocarbon to form benzene) • Benzene – Planer six carbon ring structure • 6 carbons in a planer hexagonal array • Each C has a valence of 4 – 1 with H – 2 with C (σ) – 1 free • It was thought that there were 3 double and 3 single bonds in the molecule but x ray analysis shows that the bond lengths are intermediate between single and double • The free electrons are said to be delocalised ....not involved in the direct sigma bonding of the molecule but nevertheless connected using Pi bonding • 6 valence electrons are involved in a Pi (π) bond spread between the six atoms in the ring (shared) • They form overlapped orbitals above and below the carbon ring Delocalised Pi bonding • This is the reason for the circle in the diagram Physical Properties • Non Polar means they are not soluble in water • Soluble in non polar solvents • Methylbenzene is a good solvent Occurrences and Uses • Benzene is carcinogenic • Many are not...including aspirin • Used in manufacture of dyes, detergents, herbicides and medicines • Acid – base indicators methyl Orange and Phenolphtalein are aromatic compounds Methyl Orange Homework • Draw structural formula from book • • • • • Phenolphthalein Diurin Folic Acid Morphine Martius Yellow Organic Natural products • Many examples – Include carbohydrates and Steroids – Derived from plant extracts and include perfumes, dyes, medicines – Modern techniques mean they can be isolated in pure form – Include; Aspirin, Morphine, Nicotine, Strychnine and caffine Experiment • Extraction of Clove Oil from Cloves by Steam distillation