1 / 53

AN INTRODUCTION TO ORGANIC CHEMISTRY

AN INTRODUCTION TO ORGANIC CHEMISTRY. ORGANIC CHEMISTRY. CONTENTS. Scope of organic chemistry Special nature of carbon Types of formulae Homologous series. Functional groups Nomenclature Investigating molecules. 3.1.5 Introduction to organic chemistry Nomenclature

quant
Download Presentation

AN INTRODUCTION TO ORGANIC CHEMISTRY

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. AN INTRODUCTION TO ORGANIC CHEMISTRY

  2. ORGANIC CHEMISTRY CONTENTS • Scope of organic chemistry • Special nature of carbon • Types of formulae • Homologous series • Functional groups • Nomenclature • Investigating molecules

  3. 3.1.5 Introduction to organic chemistry • Nomenclature • know and understand the terms empirical formula, molecular formula, structural formula, displayed formula, homologous series and functional group • be able to apply IUPAC rules for nomenclature to simple organic compounds, limited to chains with up to 6 carbon atoms limited in this module to alkanes, alkenes and haloalkanes • Isomerism • know and understand the meaning of the term structural isomerism • be able to draw the structures of chain and position isomers

  4. ORGANIC CHEMISTRY Organic chemistry is the study of carbon compounds. It is such a complex branch of chemistry because... 1. CARBON ATOMS FORM STRONG COVALENT BONDS TO EACH OTHER 2. CARBON ATOMS CAN BE ARRANGED IN: STRAIGHT CHAINS, BRANCHED CHAINS and RINGS 3. THE CARBON-CARBON BONDS CAN BE SINGLE, DOUBLE OR TRIPLE 4. OTHER ATOMS/GROUPS OF ATOMS CAN BE PLACED ON THE CARBON ATOMS 5. GROUPS CAN BE PLACED IN DIFFERENT POSITIONS ON A CARBON SKELETON

  5. SPECIAL NATURE OF CARBON - CATENATION 1. CARBON ATOMS FORM STRONG COVALENT BONDS TO EACH OTHER BOND ATOMIC RADIUS THE MOLECULE 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.

  6. SPECIAL NATURE OF CARBON - CATENATION 2. CARBON ATOMS CAN BE ARRANGED IN: STRAIGHT CHAINS, BRANCHED CHAINS and RINGS The ability to form bonds between atoms of the same element is called CATENATION. 3. Carbon forms chains and rings, with single, double and triple covalent bonds...

  7. THE SPECIAL NATURE OF CARBON 4. OTHER ATOMS/GROUPS OF ATOMS CAN BE PLACED ON THE CARBON ATOMS The basic atom is HYDROGEN (1 bond) but groups containing OXYGEN (2 bonds), NITROGEN (3 bonds), HALOGENS(1 bond)and SULPHUR(2 bonds) very common. CARBON SKELETON FUNCTIONAL CARBON SKELETON FUNCTIONAL GROUP GROUP The chemical reactions of an organic compound are determined by its FUNCTIONAL GROUP

  8. THE SPECIAL NATURE OF CARBON 5. 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

  9. TYPES OF FORMULAE THE EXAMPLE BEING USED IS...BUTANE MOLECULAR FORMULAC4H10 The exact numberof atoms of each element present in the molecule EMPIRICAL FORMULAC2H5 The simplest whole numberratio of atoms in the molecule

  10. TYPES OF FORMULAE Calculations… EMPIRICAL FORMULAE 1. Experimentally it was found that a compound contained 8.9g of carbon, 0.74g of hydrogen and 23.7g of oxygen. Use these results to determine the empirical formula. 1 Elements present C H O 2. Mass of each element (g) 8.9 0.74 23.7 3. RAM of each element 12 1 16 4. Moles of each element (mass/RAM) 0.74 0.74 1.48  5. Mole ratio (divide by smallest)/0.74 1 1 2 Empirical formula = CHO2

  11. TYPES OF FORMULAE Calculations… EMPIRICAL FORMULAE 2. A compound was found to contain 26.7% carbon, 2.2% hydrogen and 71.1% oxygen. Determine its empirical formula. 1 Elements present C H O 2. Mass of each element (g) 26.7 2.2 71.1 3. RAM of each element 12 1 16 4. Moles of each element (mass/RAM) 2.2 2.2 4.4  5. Mole ratio (divide by smallest)/0.74 1 1 2 Empirical formula = CHO2 Calculations… EMPIRICAL FORMULAE

  12. TYPES OF FORMULAE Calculations… MOLECULAR FORMULAE 3. A compound contains 2.67g of carbon, 0.22g of hydrogen and 7.11g of oxygen. It has a molecular mass of 90. Determine its empirical and molecular formulae. 1 Elements present C H O 2. Mass of each element (g) 2.67 0.22 7.11 3. RAM of each element 12 1 16 4. Moles of each element (mass/RAM) 0.22 0.22 0.44  5. Mole ratio (divide by smallest)/0.22 1 1 2   Empirical formula = CHO2 ‘Mr’ = 45 Actual Mr = 90 Molecular formula = (CHO2) x 2 = C2H2O4 MOLECULAR FORMULAE

  13. TYPES OF FORMULAE THE EXAMPLE BEING USED IS...BUTANE STRUCTURAL FORMULA CH3CH2CH2CH3 CH3CH(CH3)CH3 The minimal detail using conventional groups, for an unambiguous structure DISPLAYED FORMULA Shows both the relative placing of atoms and the number of bonds between them

  14. TYPES OF FORMULAE - 1 THE EXAMPLE BEING USED IS...BUTANE 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 CYCLOHEXANE THALIDOMIDE

  15. TYPES OF FORMULAE GENERAL FORMULA Represents any member of a homologous series for alkAnes it is... CnH2n+2 for alkEnes it is... CnH2n for alkYnes it is... CnH2n-2 for alcohols it is... CnH2n+1OH for carboxylic acids it is... CnH2n+1COOH

  16. HOMOLOGOUS SERIES An homologous series is 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. • e.g. alcohols CH3OH C2H5OH C3H7OH METHANOL ETHANOL PROPAN-1-OL

  17. H H H H H H C C C C C H H H H H H H H H H H C C C C C H H H H H FUNCTIONAL GROUPS There are many organic compounds... Split it into small sections for study by studying compounds which behave in a similar way... because they have a particular atom, or group of atoms, FUNCTIONAL GROUP, in their structure. NH2 OH Carbon Functional Carbon Functional skeleton Group skeleton Group = AMINE = ALCOHOL

  18. COMMON FUNCTIONAL GROUPS ALKANE ALKENE ALKYNE HALOALKANE AMINE NITRILE ALCOHOL ETHER ALDEHYDE KETONE CARBOXYLIC ACID ESTER ACYL CHLORIDE AMIDE NITRO SULPHONIC ACID

  19. COMMON FUNCTIONAL GROUPS GROUP ENDING GENERAL FORMULA EXAMPLE ALKANE - ane RH C2H6 ethane ALKENE - ene C2H4ethene ALKYNE - yne C2H2ethyne HALOALKANE halo - RX C2H5Cl chloroethane ALCOHOL - ol ROH C2H5OH ethanol ALDEHYDE -al RCHO CH3CHO ethanal KETONE - one RCOR CH3COCH3propanone CARBOXYLIC ACID - oic acid RCOOH CH3COOH ethanoicacid ACYL CHLORIDE - oyl chloride RCOCl CH3COCl ethanoylchloride AMIDE - amide RCONH2 CH3CONH2ethanamide ESTER - yl - oate RCOOR CH3COOCH3methylethanoate NITRILE - nitrile RCN CH3CN ethanenitrile AMINE - amine RNH2 CH3NH2 methylamine NITRO nitro- RNO2 CH3NO2nitromethane SULPHONIC ACID - sulphonic acid RSO3H C6H5SO3H benzenesulphonic acid ETHER - oxy - ane ROR C2H5OC2H5ethoxyethane

  20. 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. C2H6 C3H7Br C4H8 C2H6O C3H6O C2H7N C2H4O2 C2H3N

  21. 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. covalent bonds surrounding them carbon atoms have 4 oxygen atoms 2 nitrogen atoms 3 hydrogen and halogen atoms 1

  22. HOW MANY STRUCTURES? C2H6 ONE C3H7Br TWO C4H8 FIVE -3 with C=C and 2 ring compounds with all C-C’s C2H6O TWO - 1 with C-O-C and 1 with C-O-H C3H6O SIX - 2 with C=O, 2 with C=C and 2 with rings C2H7N TWO C2H4O2 SEVERAL - Only 2 are stable C2H3N TWO

  23. NOMENCLATURE There are two types of naming system commonly found in organic chemistry; Trivial: based on some property or historical aspect; tells you little about the structure Systematic : based on an agreed set of rules (I.U.P.A.C); exact structure can be found from the name (and vice-versa).

  24. I.U.P.A.C. NOMENCLATURE A systematic name has two main parts. STEM - number of C atoms in the longest chain bearing the functional group shown by a prefix numbering the chain allows position and identity of any side-chains to be indicated Prefix C atoms Alkane meth- 1 methane eth- 2 ethane prop- 3 propane but- 4 butane pent- 5 pentane Prefix C atoms Alkane hex- 6 hexane hept- 7 heptane oct- 8 octane non- 9 nonane dec- 10 decane The ending-ane is the same as they are all alkanes.

  25. I.U.P.A.C. NOMENCLATURE SUFFIXan ending – gives the functional group present Relevant ending added to the basic stem. Position of the functional group must be given. -ene -yne -amine -nitrile -ol -oic acid 1-CHLOROBUTANE 2-CHLOROBUTANE

  26. I.U.P.A.C. NOMENCLATURE Working out how long a chain is. Organic molecules are three dimensional... paper is two dimensional, so... it can be confusing when comparing molecules because... 1. It is too complicated to draw molecules with the correct bond angles 2. Single covalent bonds are free to rotate

  27. CH3 CH3 CH2 CH2 CH2 CH3 CH3 CH2 CH3 CH2 CH2 CH3 CH2 CH2 CH2 CH3 CH2 CH2 CH2 CH3 I.U.P.A.C. NOMENCLATURE All the following written structures are of the same molecule - PENTANE C5H12 5 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.

  28. CH3 CH3 CH3 CH2 CH2 CH2 CH CH3 CH2 CH3 CH CH2 CH3 CH3 CH3 CH3 CH2 CH CH2 CH CH3 I.U.P.A.C. NOMENCLATURE Working out how long a chain is. Look at the structures and work out how many carbon atoms are in the longest chain. 4 4 5 3 6 6 5 5 4 6 4 6

  29. I.U.P.A.C. NOMENCLATURE SUBSTITUENTS Many compounds have substituents (additional atoms, or groups) attached to the chain. Their position is numbered. 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 CH3 - CH3 ethyl CH3- CH2- C2H5 propyl CH3- CH2- CH2- C3H7

  30. CH3 CH3 CH CH3 CH2 CH2 CH2 CH3 CH CH2 CH3 CH2 CH2 CH I.U.P.A.C. NOMENCLATURE Number the longest chain from one end to give the lowest numbers. Side-chain names appear in alphabetical order butyl, ethyl, methyl, propyl Eachside-chain is given its own number. If identical side-chains appear more than once, prefix with di, tri, tetra, penta, hexa Numbers are separated from names by a HYPHEN e.g. 2-methylheptane Numbers are separated from numbers by a COMMA e.g. 2,3-dimethylbutane 7 8 8 6 5 Example

  31. CH3 CH3 CH CH3 CH2 CH2 CH2 CH3 CH CH2 CH3 CH2 CH2 CH I.U.P.A.C. NOMENCLATURE Example longest chain 8 (it is an octane) 8 1 2 4 Red numbering gives: 3 8 7 6 5 5 7 8 6 methyl on 4 Sum of numbers = 15 4 3 1 2 propyl on 5 3-ethyl-5-methyl-4-propyloctane ethyl on 6 Green numbering gives: ethyl on 3 Sum of numbers = 12 propyl on 4 methyl on 5 Put in alphabetical order:

  32. CH3 CH3 CH3 CH2 CH2 CH2 CH CH3 CH2 CH3 CH CH2 CH3 CH3 CH3 CH3 CH2 CH CH2 CH CH3 I.U.P.A.C. NOMENCLATURE Apply the rules and name these alkanes

  33. CH3 CH3 CH3 CH2 CH2 CH2 CH CH3 CH2 CH3 CH CH2 CH3 CH3 CH3 CH3 CH2 CH CH2 CH CH3 I.U.P.A.C. NOMENCLATURE Apply the rules and name these alkanes Longest chain = 5 so it is a pentane A -CH3, group is attached to the third carbon from one end… methyl 3-methylpentane Longest chain = 6 so it is a hexane A -CH3, methyl, group is attached to the second carbon from one end… 2-methylhexane Longest chain = 6 so it is a hexane -CH3, methyl, groups are attached to the third and fourth carbon atoms (whichever end you count from 3,4-dimethylhexane

  34. 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 pent-2-ene(NOT pent-3-ene)

  35. NAMING ALKENES Side-chain Similar to alkanes position is based on the number allocated to the double bond 1 2 3 4 1 2 3 4 CH2 = CH(CH3)CH2CH3CH2 =CHCH(CH3)CH3 2-methylbut-1-ene3-methylbut-1-ene

  36. 1 2 C H C H 3 3 C H C C C H C H C H 3 2 C H C H 2 3 3

  37. Two methyl groups on the same C atom 1 1 2 3 4 5 5 C atoms 5 4 3 2 1 Identify the longest chain containing the double bond Number the chain with the C’s of the double bond having the lowest numbers Identify the side chains and where they are. 3,3-dimethylpent-1-ene

  38. 2

  39. C H C H 3 3 C H C C C H C H C H 3 2 C H C H 2 3 3

  40. ISOMERISM

  41. TYPES OF ISOMERISM CHAIN ISOMERISM STRUCTURAL ISOMERISM POSITION ISOMERISM Same molecular formula but different structural formulae FUNCTIONAL GROUP ISOMERISM STEREOISOMERISM

  42. 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

  43. STRUCTURAL ISOMERISM - INTRODUCTION COMPOUNDS HAVE THE SAME MOLECULAR FORMULA BUT DIFFERENT STRUCTURAL FORMULA • FunctionalGroup 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

  44. STRUCTURAL ISOMERISM - CHAIN 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

  45. STRUCTURAL ISOMERISM - CHAIN DIFFERENCES BETWEEN CHAIN ISOMERS ChemicalIsomers show similar chemical properties because the same functional group is present. Physical Properties such as density and boiling point show trends according to 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 straight chain - 11.7°C branched greater branching = lower boiling point

  46. STRUCTURAL ISOMERISM - POSITIONAL 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.

  47. STRUCTURAL ISOMERISM - POSITIONAL 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

  48. STRUCTURAL ISOMERISM - POSITIONAL Example 3 RELATIVE POSITIONS ON A BENZENE RING 1,2-DICHLOROBENZENE ortho dichlorobenzene 1,3-DICHLOROBENZENE meta dichlorobenzene 1,4-DICHLOROBENZENE para dichlorobenzene

  49. STRUCTURAL ISOMERISM – FUNCTIONAL GROUP ALCOHOLS and ETHERS ALDEHYDES and KETONES ACIDS and ESTERS

  50. STRUCTURAL ISOMERISM – FUNCTIONAL GROUP ALCOHOLS and ETHERS NameETHANOL METHOXYMETHANE ClassificationALCOHOLETHER Functional GroupR-OHR-O-R Physical propertiespolar O-H bond gives rise No hydrogen bonding to hydrogen bonding. low boiling point get higher boiling point insoluble in water and solubility in water Chemical properties Lewis base Inert Wide range of reactions

More Related