Organic Chemistry Nomenclature and Structures

INTRODUCTION TO ORGANIC CHEMISTRY - NOMENCLATURE Learning Objectives: 1. Describe how organic compounds can be represented by empirical, molecular, general, structural, displayed and skeletal formulae. 2. Explain how IUPAC rules are used to name and draw the structures of organic compounds limited to chains and rings with up to six carbon atoms each. 3. Identify and evaluate different methods for the structural identification of organic molecules. Specification Reference: 3.3.1.1

ORGANIC CHEMISTRY Organic chemistry is the study of carbon compounds. It is such a complex branch of chemistry because... CARBON ATOMS FORM STRONG COVALENT BONDS TO EACH OTHER THE CARBON-CARBON BONDS CAN BE SINGLE, DOUBLE OR TRIPLE STRAIGHT CHAINS BRANCHED CHAINS and RINGS CARBON ATOMS CAN BE ARRANGED IN OTHER ATOMS/GROUPS OF ATOMS CAN BE PLACED ON THE CARBON ATOMS GROUPS CAN BE PLACED IN DIFFERENT POSITIONS ON A CARBON SKELETON LO1: Describe how organic compounds can be represented by empirical, molecular, general, structural, displayed and skeletal formulae.

SPECIAL NATURE OF CARBON - CATENATION CATENATION is the ability to form bonds between atoms of the same element. Carbon forms chains and rings, with single, double and triple covalent bonds, becauseit is able toFORM STRONG COVALENT BONDS WITH OTHER CARBON ATOMS Carbon forms a vast number of carbon compounds because of the strength of the C-C covalent bond. Other Group IV elements can do it but their chemistry is limited due to the weaker bond strength. BOND ATOMIC RADIUS BOND ENTHALPY C-C 0.077 nm +348 kJmol-1 Si-Si 0.117 nm +176 kJmol-1 The larger the atoms, the weaker the bond. Shielding due to filled inner orbitals and greater distance from the nucleus means that the shared electron pair is held less strongly. LO1: Describe how organic compounds can be represented by empirical, molecular, general, structural, displayed and skeletal formulae.

THE SPECIAL NATURE OF CARBON CHAINSANDRINGS CARBON ATOMS CAN BE ARRANGED IN STRAIGHT CHAINS BRANCHED CHAINS and RINGS You can also get a combination of rings and chains LO1: Describe how organic compounds can be represented by empirical, molecular, general, structural, displayed and skeletal formulae.

THE SPECIAL NATURE OF CARBON MULTIPLE BONDING AND SUBSTITUENTS CARBON-CARBON COVALENT BONDS CAN BE SINGLE, DOUBLE OR TRIPLE DIFFERENT ATOMS / GROUPS OF ATOMS CAN BE PLACED ON THE CARBONS The basic atom is HYDROGEN but groups containing OXYGEN, NITROGEN, HALOGENS and SULPHUR are very common. CARBON SKELETON FUNCTIONAL CARBON SKELETON FUNCTIONAL GROUP GROUP The chemistry of an organic compound is determined by its FUNCTIONAL GROUP LO1: Describe how organic compounds can be represented by empirical, molecular, general, structural, displayed and skeletal formulae.

THE SPECIAL NATURE OF CARBON MULTIPLE BONDING AND SUBSTITUENTS ATOMS/GROUPS CAN BE PLACED IN DIFFERENT POSITIONS ON A CARBON SKELETON THE C=C DOUBLE BOND IS IN A DIFFERENT POSITION PENT-1-ENE PENT-2-ENE THE CHLORINE ATOM IS IN A DIFFERENT POSITION 1-CHLOROBUTANE 2-CHLOROBUTANE LO1: Describe how organic compounds can be represented by empirical, molecular, general, structural, displayed and skeletal formulae.

TYPES OF FORMULAE - 1 C4H10 MOLECULAR FORMULA The exact number of atoms of each element present in the molecule THE EXAMPLE BEING USED IS... BUTANE C2H5 EMPIRICAL FORMULA The simplest whole numberratio of atoms in the molecule CH3CH2CH2CH3 CH3CH(CH3)CH3 STRUCTURAL FORMULA The minimal detail using conventional groups, for an unambiguous structure there are two possible structures DISPLAYED FORMULA Shows both the relative placing of atoms and the number of bonds between them H H H H H H H H C C C C H H C C C H H H H C H H H H H H LO1: Describe how organic compounds can be represented by empirical, molecular, general, structural, displayed and skeletal formulae.

TYPES OF FORMULAE - 2 SKELETAL FORMULA A skeletal formula is used to show a simplified organic formula by removing hydrogen atoms from alkyl chains, leaving just a carbon skeleton and associated functional groups CH2 CH2 CH2 for CH2 CH2 CH2 CYCLOHEXANE THALIDOMIDE GENERAL FORMULA Represents any member of a homologous series for alkanes it is... CnH2n+2 possibleformulae... CH4, C2H6 .... C99H200 The formula does not apply to cyclic compounds such as cyclohexane is C6H12 - by joining the atoms in a ring you need fewer H s LO1: Describe how organic compounds can be represented by empirical, molecular, general, structural, displayed and skeletal formulae.

HOMOLOGOUS SERIES A series of compounds of similar structure in which each member differs from the next by a common repeating unit, CH2. Series members are calledhomologuesand... all share the same general formula. formula of a homologue differs from its neighbour by CH2. (e.g. CH4, C2H6, ... etc ) contain the same functional group have similar chemical properties. show a gradual change in physical properties as molar mass increases. can usually be prepared by similar methods. ALCOHOLS - FIRST THREE MEMBERS OF THE SERIES CH3OH METHANOL C2H5OH ETHANOL C3H7OH PROPAN-1-OL LO1: Describe how organic compounds can be represented by empirical, molecular, general, structural, displayed and skeletal formulae.

FUNCTIONAL GROUPS Organic chemistry is a vast subject so it is easier to split it into small sections for study. This is done by studying compounds which behave in a similar way because they have a particular atom, or group of atoms, FUNCTIONAL GROUP, in their structure. Functional groups can consist of one atom, a group of atoms or multiple bonds between carbon atoms. Each functional group has its own distinctive properties which means that the properties of a compound are governed by the functional group(s) in it. H H H H H H H H H H H C C C C C OH H C C C C C NH2 H H H H H H H H H H Carbon skeleton Functional Group = AMINE Carbon Functional skeleton Group = ALCOHOL LO1: Describe how organic compounds can be represented by empirical, molecular, general, structural, displayed and skeletal formulae.

COMMON FUNCTIONAL GROUPS GROUP ENDING GENERAL FORMULA EXAMPLE ethane ALKANE - ane RH C2H6 C2H4 C2H2 C2H5Cl C2H5OH CH3CHO CH3COCH3propanone CH3COOH ethanoicacid CH3COCl ethanoylchloride CH3CONH2ethanamide CH3COOCH3methylethanoate CH3CN ethanenitrile CH3NH2 methylamine CH3NO2 nitromethane C6H5SO3H benzenesulphonic acid C2H5OC2H5ethoxyethane ethene ALKENE - ene ethyne ALKYNE - yne chloroethane HALOALKANE halo - RX ethanol ALCOHOL - ol ROH ethanal ALDEHYDE -al RCHO KETONE - one RCOR CARBOXYLIC ACID - oic acid RCOOH ACYL CHLORIDE - oyl chloride RCOCl AMIDE - amide RCONH2 RCOOR ESTER - yl - oate NITRILE - nitrile RCN AMINE - amine RNH2 RNO2 RSO3H ROR NITRO nitro- SULPHONIC ACID - sulphonic acid ETHER - oxy - ane LO1: Describe how organic compounds can be represented by empirical, molecular, general, structural, displayed and skeletal formulae.

COMMON FUNCTIONAL GROUPS ALKANE CARBOXYLIC ACID ALKENE ALKYNE ESTER HALOALKANE ACYL CHLORIDE AMINE NITRILE AMIDE ALCOHOL ETHER NITRO ALDEHYDE SULPHONIC ACID KETONE LO1: Describe how organic compounds can be represented by empirical, molecular, general, structural, displayed and skeletal formulae.

HOW MANY STRUCTURES? Draw legitimate structures for each molecular formula and classify each one according to the functional group present. Not all the structures represent stable compounds. carbon atoms have oxygen atoms nitrogen atoms hydrogen halogen atoms 4 covalent bonds surrounding them 2 3 1 1 C2H6 C3H7Br C4H8 C2H6O C3H6O C2H7N C2H4O2 C2H3N ONE TWO FIVE -3 with C=C and 2 ring compounds with all C-C s TWO - 1 with C-O-C and 1 with C-O-H SIX - 2 with C=O, 2 with C=C and 2 with rings TWO SEVERAL - Only 2 are stable TWO LO1: Describe how organic compounds can be represented by empirical, molecular, general, structural, displayed and skeletal formulae.

NOMENCLATURE Ideally a naming system should tell you everything about a structure without ambiguity. There are two types of naming system commonly found in organic chemistry; Trivial : Systematic : based on some property or historical aspect; the name tells you little about the structure based on an agreed set of rules (I.U.P.A.C); exact structure can be found from the name (and vice-versa). HOMOLOGOUS SERIES trivial name systematic name example(s) paraffin alkane olefin alkene fatty acid alkanoic (carboxylic) acid methane, butane ethene, butene ethanoic acid INDIVIDUAL COMPOUNDS derivation methu = wine (Gk.) butyrum = butter (Lat.) acetum = vinegar (Lat.) trivial name methane butane acetic acid systematic name methane (CH4) butane (C4H10) ethanoic acid (CH3COOH) LO2: Explain how IUPAC rules are used to name and draw the structures of organic compounds limited to chains and rings with up to six carbon atoms each.

I.U.P.A.C. NOMENCLATURE A systematic name has two main parts. number of carbon atoms in longest chain bearing the functional group + a prefix showing the position and identity of any side-chain substituents. STEM Apart from the first four, which have trivial names, the number of carbons atoms is indicated by a prefix derived from the Greek numbering system. Prefix C atoms meth- eth- prop- but- pent- hex- hept- oct- non- dec- 10 Alkane methane ethane propane butane pentane hexane heptane octane nonane decane 1 2 3 4 5 6 7 8 9 The list of alkanes demonstrate the use of prefixes. The ending -ane is the same as they are all alkanes. Working out which is the longest chain can pose a problem with larger molecules. LO2: Explain how IUPAC rules are used to name and draw the structures of organic compounds limited to chains and rings with up to six carbon atoms each.

I.U.P.A.C. NOMENCLATURE How long is a chain? Because organic molecules are three dimensional and paper is two dimensional it can confusing when comparing molecules. This is because... 1. It is too complicated to draw molecules with the correct bond angles 2. Single covalent bonds are free to rotate All the following written structures are of the same molecule - PENTANE C5H12 CH3 CH3 CH2CH2CH3 CH2 CH3 CH2 CH2CH2 CH3 CH3 CH3 CH2 CH2 CH2CH2 CH2 CH2 CH3 A simple way to check is to run a finger along the chain and see how many carbon atoms can be covered without reversing direction or taking the finger off the page. In all the above there are... FIVE CARBON ATOMS IN A LINE. LO2: Explain how IUPAC rules are used to name and draw the structures of organic compounds limited to chains and rings with up to six carbon atoms each.

I.U.P.A.C. NOMENCLATURE How long is the longest chain? Look at the structures and work out how many carbon atoms are in the longest chain. CH3 CH2 CH3 CH CH2 CH3 CH3 CH3 CH3 CH2 CH2CH2 CH CH3 CH3 CH2 CH3 CH CH3 CH2 CH LO2: Explain how IUPAC rules are used to name and draw the structures of organic compounds limited to chains and rings with up to six carbon atoms each.

I.U.P.A.C. NOMENCLATURE A systematic name has two main parts. SUFFIXAn ending that tells you which functional group is present See if any functional groups are present. Add relevant ending to the basic stem. Functional group ALKANE ALKENE ALKYNE ALCOHOL ALDEHYDE KETONE ACID Suffix - ANE - ENE - YNE - OL - AL - ONE - OIC ACID In many cases the position of the functional group must be given to avoid any ambiguity 1-CHLOROBUTANE 2-CHLOROBUTANE SUBSTITUENTS Many compounds have substituents (additional atoms, or groups) attached to the chain. Their position is numbered. LO2: Explain how IUPAC rules are used to name and draw the structures of organic compounds limited to chains and rings with up to six carbon atoms each.

I.U.P.A.C. NOMENCLATURE SIDE-CHAINcarbon based substituents are named before the chain name. they have the prefix -yl added to the basic stem (e.g. CH3 is methyl). Alkyl radicals methyl ethyl propyl CH3 - CH3- CH2- CH3- CH2- CH2- CH3 C2H5 C3H7 Number the principal chain from one end to give the lowest numbers. Side-chain names appear in alphabetical orderbutyl, ethyl, methyl, propyl Eachside-chain is given its own number. If identical side-chains appear more than once, prefix withdi, tri, tetra, penta, hexa Numbers are separated from names by a HYPHEN Numbers are separated from numbers by a COMMA e.g. 2-methylheptane e.g. 2,3-dimethylbutane Example longest chain 8 (it is an octane) 3,4,6 are the numbers NOT 3,5,6 order is ethyl, methyl, propyl 3-ethyl-5-methyl-4-propyloctane CH3 CH2 CH3 CH CH3 CH2 CH2 CH3 CH CH2 CH3 CH2 CH2 CH LO2: Explain how IUPAC rules are used to name and draw the structures of organic compounds limited to chains and rings with up to six carbon atoms each.

I.U.P.A.C. NOMENCLATURE Apply the rules and name these alkanes CH3 CH2 CH3 CH CH2 CH3 CH3 CH3 CH3 CH2 CH2CH2 CH CH3 CH3 CH2 CH3 CH CH3 CH2 CH LO2: Explain how IUPAC rules are used to name and draw the structures of organic compounds limited to chains and rings with up to six carbon atoms each.

NAMING ALKENES Length In alkenes the principal chain is not always the longest chain It must contain the double bond the name ends in -ENE PositionCount from one end as with alkanes. Indicated by the lower numbered carbon atom on one end of the C=C bond 5 4 3 2 1 CH3CH2CH=CHCH3 is pent-2-ene (NOT pent-3-ene) Side-chain Similar to alkanes position is based on the number allocated to the double bond 1 2 3 4 CH2 = CH(CH3)CH2CH3CH2 = CHCH(CH3)CH3 2-methylbut-1-ene 1 2 3 4 3-methylbut-1-ene LO2: Explain how IUPAC rules are used to name and draw the structures of organic compounds limited to chains and rings with up to six carbon atoms each.

WHICH COMPOUND IS IT? Elucidation of the structures of organic compounds - a brief summary Organic chemistry is so vast that the identification of a compound can be involved. The characterisation takes place in a series of stages (see below). Relatively large amounts of substance were required to elucidate the structure but, with modern technology and the use of electronic instrumentation, very small amounts are now required. Elemental composition One assumes that organic compounds contain carbon and hydrogen but it can be proved by letting the compound undergo combustion. Carbon is converted to carbon dioxide and hydrogen is converted to water. Percentage composition by mass Found by dividing the mass of an element present by the mass of the compound present, then multiplying by 100. Elemental mass of C and H can be found by allowing the substance to undergo complete combustion. From this one can find... mass of carbon mass of hydrogen = = 12/44 of the mass of CO2 produced 2/18 of the mass of H2O produced LO3: Identify and evaluate different methods for the structural identification of organic molecules.

INVESTIGATING MOLECULES Empirical formula The simplest ratio of elements present in the substance. It is calculated by dividing the mass or percentage mass of each element by its molar mass and finding the simplest ratio between the answers. Empirical formula is converted to the molecular formula using molecular mass. Molecular mass Traditionally found out using a variety of techniques such as ... volumetric analysis or molar volume methods (Dumas, Victor-Meyer or gas syringe experiments). Mass spectrometry is now used. The m/z value of the molecular ion and gives the molecular mass. The fragmentation pattern gives information about the compound. Molecular formula The molecular formula is an exact multiple of the empirical formula. Comparing the molecular mass with the empirical mass allows one to find the true formula. e.g. if the empirical formula is CH (relative mass = 13) and the molecular mass is 78 the molecular formula will be 78/13 or 6 times the empirical formula i.e. C6H6 . Structural formula Because of the complexity of organic molecules, there can be more than one structure for a given molecular formula. To work out the structure, different tests are carried out. LO3: Identify and evaluate different methods for the structural identification of organic molecules.

INVESTIGATING MOLECULES Chemical Chemical reactions can identify the functional group(s) present. Spectroscopy IR detects bond types due to absorbance of i.r. radiation NMR gives information about the position and relative numbers of hydrogen atoms present in a molecule Confirmation By comparison of IR or NMR spectra and mass spectrometry LO3: Identify and evaluate different methods for the structural identification of organic molecules.

INTRODUCTION TO ORGANIC CHEMISTRY - MECHANISMS Learning Objectives: 1. Identify the different species involved in organic reactions. 2. Describe how arrows are used to show how bonds are broken and formed. 3. Explain how reaction mechanisms are used to show the movement of electron pairs. Specification Reference: 3.3.1.2

MEET THE ATTACKERS LO1: Identify the different species involved in organic reactions.

WHO IS ATTACKED? THE BONDING IN A MOLECULE INFLUENCES WHAT WILL ATTACK IT A typical covalent bond with one shared pair nothing to tempt an attacking species SINGLE Bond has twice as many electrons species which like electrons will be attracted MULTIPLE Similar atoms have an equal attraction for the shared pair of the covalent bond NON-POLAR + + Atoms have different electronegativities and the shared pair will be attracted more to one end species known as nucleophiles will be attracted to the slightly positive end POLAR LO1: Identify the different species involved in organic reactions.

WHAT ATTACKS ALKANES? ALKANES ARE RELATIVELY UNREACTIVE ORGANIC COMPOUNDS ALKANES CONTAIN TWO BOND TYPES C-H and C-C Both bonds are single no electron rich areas Bonds are non-polar - no electron deficient areas Free radicals are very reactive and do attack FREE RADICAL SUBSTITUTION LO1: Identify the different species involved in organic reactions.

WHAT ATTACKS ALKENES? ALKENES ARE MUCH MORE REACTIVE THAN ALKANES ALKENES CONTAIN A C=C BOND There will be twice as many electrons between the carbon atoms as there are in a single bond C=C bond is double an electron rich area Bonds are non-polar - no electron deficient areas ELECTROPHILIC ADDITION LO1: Identify the different species involved in organic reactions.

WHAT ATTACKS HALOGENOALKENES? HALOGENOALKANES ARE MUCH MORE REACTIVE THAN ALKANES HALOGENOALKANES CONTAIN A POLAR BOND The halogen is more electronegative than the carbon attracts the shared electron pair. + + Bond is single not an electron rich area Bond is polar the greater electronegativity of the halogen creates a dipole making the carbon atom electron deficient. NUCLEOPHILIC SUBSTITUTION LO1: Identify the different species involved in organic reactions.

CURLY ARROWS THESE ARE USED TO REPRESENT THE MOVEMENT OF ELECTRONS ELECTRONS MOVE FROM AREAS OF HIGH ELECTRON DENSITY TO ONES WITH A LOWER ELECTRON DENSITY For example from LONE PAIRS DOUBLE BONDS to POSITIVE SPECIES THE + + END OF POLAR BONDS LO2: Describe how arrows are used to show how bonds are broken and formed. LO3: Explain how reaction mechanisms are used to show the movement of electron pairs.

CURLY ARROWS THESE ARE USED TO REPRESENT THE MOVEMENT OF ELECTRONS ARROWS WITH TWO HEADS INDICATE THE MOVEMENT OF TWO (A PAIR OF) ELECTRONS A PAIR of electrons moves from here to here ARROWS WITH ONE HEAD INDICATE THE MOVEMENT OF JUST ONE ELECTRON ONE electron moves from here to here ALWAYS BE PRECISE WITH THE POSITIONING OF ANY ARROWS LO2: Describe how arrows are used to show how bonds are broken and formed. LO3: Explain how reaction mechanisms are used to show the movement of electron pairs.

DRAWING CURLY ARROWS NUCLEOPHILES:- possess a lone pair of electrons lone pair negative charge H O HYDROXIDE ION more lone pairs H AMMONIA MOLECULE H N lone pair Nucleophiles don t need to have negative charge BUT they must have a lone pair H LO2: Describe how arrows are used to show how bonds are broken and formed. LO3: Explain how reaction mechanisms are used to show the movement of electron pairs.

DRAWING CURLY ARROWS ELECTROPHILES:- attract a lone pair of electrons There are no electrons in the outer shell of hydrogen so it has space to accept two electrons H HYDROGEN ION + + contains a POLAR BOND; the + + end will attract the electron pair HYDROGEN CHLORIDE H Cl LO2: Describe how arrows are used to show how bonds are broken and formed. LO3: Explain how reaction mechanisms are used to show the movement of electron pairs.

DRAWING CURLY ARROWS BALANCING THE BOOKS When moving electrons about, it is essential to check that the charges on the reactants and products balance. H H + + H O H C C Br 3 H H C C O H 3 H Br This is the basic mechanism for the nucleophilic substitution of bromoethane. To see how it works, it helps to show the electrons involved. LO2: Describe how arrows are used to show how bonds are broken and formed. LO3: Explain how reaction mechanisms are used to show the movement of electron pairs.

DRAWING CURLY ARROWS BALANCING THE BOOKS When moving electrons about, it is essential to check that the charges on the reactants and products balance. H H H O H C C Br 3 H H C C O H 3 H Br LO2: Describe how arrows are used to show how bonds are broken and formed. LO3: Explain how reaction mechanisms are used to show the movement of electron pairs.

INTRODUCTION TO ORGANIC CHEMISTRY - ISOMERISM Learning Objectives: 1. State the meaning of the term structural isomers, identifying examples from organic structures. 2. Describe the differences between chain, position and functional group isomers, giving appropriate examples. 3. Explain the meaning of the term stereoisomerism using E/Z isomerism as an example by application of the Cahn-Ingold- Prelog priority rules. Specification Reference: 3.3.1.3

TYPES OF ISOMERISM CHAIN ISOMERISM STRUCTURAL ISOMERISM POSITION ISOMERISM Same molecular formula but different structural formulae FUNCTIONAL GROUP ISOMERISM GEOMETRICAL ISOMERISM Occurs due to the restricted rotation of C=C double bonds... two forms E and Z (CIS and TRANS) STEREOISOMERISM Same molecular formula but atoms occupy different positions in space. OPTICAL ISOMERISM Occurs when molecules have a chiral centre. Get two non- superimposable mirror images. LO1: State the meaning of the term structural isomers, identifying examples from organic structures.

STRUCTURAL ISOMERISM - INTRODUCTION COMPOUNDS HAVE THE SAME MOLECULAR FORMULA BUT DIFFERENT STRUCTURAL FORMULA Chain different arrangements of the carbon skeleton similar chemical properties slightly different physical properties more branching = lower boiling point Positional same carbon skeleton same functional group functional group is in a different position similar chemical properties - slightly different physical properties Functional Group different functional group different chemical properties different physical properties Sometimes more than one type of isomerism occurs in the same molecule. The more carbon atoms there are, the greater the number of possible isomers LO1: State the meaning of the term structural isomers, identifying examples from organic structures. LO2: Describe the differences between chain, position and functional group isomers, giving appropriate examples.

STRUCTURAL ISOMERISM - CHAIN caused by different arrangements of the carbon skeleton similar chemical properties slightly different physical properties more branching = lower boiling point There are two structural isomers of C4H10. One is a straight chain molecule where all the carbon atoms are in a single row. The other is a branched molecule where three carbon atoms are in a row and one carbon atom sticks out of the main chain. BUTANE straight chain 2-METHYLPROPANE branched C4H10 LO1: State the meaning of the term structural isomers, identifying examples from organic structures. LO2: Describe the differences between chain, position and functional group isomers, giving appropriate examples.

STRUCTURAL ISOMERISM - CHAIN DIFFERENCES BETWEEN CHAIN ISOMERS Chemical Isomers show similar chemical properties because the same functional group is present. Physical Properties such as density and boiling point show trends according to the of the degree of branching Boiling Point straight chain isomers have higher values than branched ones the greater the degree of branching the lower the boiling point branching decreases the effectiveness of intermolecular forces less energy has to be put in to separate the molecules - 0.5 C - 11.7 C branched greater branching = lower boiling point straight chain LO1: State the meaning of the term structural isomers, identifying examples from organic structures. LO2: Describe the differences between chain, position and functional group isomers, giving appropriate examples.

STRUCTURAL ISOMERISM - POSITIONAL molecule has the same carbon skeleton molecule has the same same functional group... BUT the functional group is in a different position have similar chemical properties / different physical properties Example 1 POSITION OF A DOUBLE BOND IN ALKENES 1 2 2 3 PENT-1-ENE double bond between carbons 1 and 2 PENT-2-ENE double bond between carbons 2 and 3 There are no other isomers with five C s in the longest chain but there are three other structural isomers with a chain of four carbons plus one in a branch. LO1: State the meaning of the term structural isomers, identifying examples from organic structures. LO2: Describe the differences between chain, position and functional group isomers, giving appropriate examples.

STRUCTURAL ISOMERISM - POSITIONAL molecule has the same carbon skeleton molecule has the same same functional group... BUT the functional group is in a different position have similar chemical properties / different physical properties Example 2 POSITION OF A HALOGEN IN A HALOALKANE BUT 1 2 2 1-CHLOROBUTANE halogen on carbon 1 2-CHLOROBUTANE halogen on carbon 2 is NOT 3-CHLOROBUTANE Moving the chlorine along the chain makes new isomers; the position is measured from the end nearest the functional group... the third example is 2- NOT 3-chlorobutane. There are 2 more structural isomers of C4H9Cl but they have a longest chain of 3 LO1: State the meaning of the term structural isomers, identifying examples from organic structures. LO2: Describe the differences between chain, position and functional group isomers, giving appropriate examples.

STRUCTURAL ISOMERISM - POSITIONAL molecule has the same carbon skeleton molecule has the same same functional group... BUT the functional group is in a different position have similar chemical properties / different physical properties Example 3 RELATIVE POSITIONS ON A BENZENE RING 1,2-DICHLOROBENZENE ortho dichlorobenzene 1,3-DICHLOROBENZENE meta dichlorobenzene 1,4-DICHLOROBENZENE para dichlorobenzene LO1: State the meaning of the term structural isomers, identifying examples from organic structures. LO2: Describe the differences between chain, position and functional group isomers, giving appropriate examples.

STRUCTURAL ISOMERISM FUNCTIONAL GROUP molecules have same molecular formula molecules have different functional groups molecules have different chemical properties molecules have different physical properties ALCOHOLS and ETHERS ALDEHYDES and KETONES ACIDS and ESTERS LO1: State the meaning of the term structural isomers, identifying examples from organic structures. LO2: Describe the differences between chain, position and functional group isomers, giving appropriate examples.

STRUCTURAL ISOMERISM FUNCTIONAL GROUP ALCOHOLS and ETHERS Name ETHANOL METHOXYMETHANE Classification ALCOHOL ETHER Functional Group R-OH R-O-R Physical properties polar O-H bond gives rise to hydrogen bonding. get higher boiling point and solubility in water No hydrogen bonding low boiling point insoluble in water Chemical properties Lewis base Wide range of reactions Inert LO1: State the meaning of the term structural isomers, identifying examples from organic structures. LO2: Describe the differences between chain, position and functional group isomers, giving appropriate examples.

STRUCTURAL ISOMERISM FUNCTIONAL GROUP ALDEHYDES and KETONES Name PROPANAL PROPANONE Classification ALDEHYDE KETONE FunctionalGroup R-CHO R-CO-R Physicalproperties Chemical properties polar C=O bond gives dipole-dipole interaction polar C=O bond gives dipole-dipole interaction easily oxidised to acids of undergo oxidation under same number of carbons extreme conditions only reduced to 1 alcohols reduced to 2 alcohols LO1: State the meaning of the term structural isomers, identifying examples from organic structures. LO2: Describe the differences between chain, position and functional group isomers, giving appropriate examples.

STRUCTURAL ISOMERISM FUNCTIONAL GROUP CARBOXYLIC ACIDS and ESTERS Name PROPANOIC ACID METHYL ETHANOATE Classification CARBOXYLIC ACID ESTER Functional Group R-COOH R-COOR Physical properties Chemical properties O-H bond gives rise to hydrogen bonding. get higher boiling point and solubility in water No hydrogen bonding insoluble in water acidic react with alcohols fairly unreactive hydrolysed to acids LO1: State the meaning of the term structural isomers, identifying examples from organic structures. LO2: Describe the differences between chain, position and functional group isomers, giving appropriate examples.

STEREOISOMERISM Molecules have the SAMEMOLECULARFORMULA but the atoms are joined to each other in a DIFFERENT SPACIAL ARRANGEMENT - they occupy a different position in 3-dimensional space. There are two types... GEOMETRICAL ISOMERISM OPTICAL ISOMERISM LO3: Explain the meaning of the term stereoisomerism using E/Z isomerism as an example by application of the Cahn-Ingold-Prelog priority rules.

GEOMETRICAL ISOMERISM IN ALKENES Introduction an example of stereoisomerism found in some, but not all, alkenes occurs due to the RESTRICTED ROTATION OF C=C bonds get two forms... CIS (Z) TRANS (E) Groups/atoms are on the SAME SIDE of the double bond Groups/atoms are on OPPOSITE SIDES across the double bond LO3: Explain the meaning of the term stereoisomerism using E/Z isomerism as an example by application of the Cahn-Ingold-Prelog priority rules.