NAMING Organic Chemistry IUPAC

L.O -recognise the common functional groups -understand and be able to use the IUPAC nomenclature -understand the formation of homologous series and the similarity of properties -understand why isomerism occurs and be able to draw isomers for given molecular formulas -understand the formation of sigma and pi bonds and know their occurrence and the implication for molecular shapes -understand the concept of saturation and apply it to the alkanes as a ‘base’ homologous series -recognise the importance of alkanes as fuels, their combustion products and the environmental effects of burning hydrocarbon fuels -recall details of the fractionation of oil and the uses of the fractions -understand homolytic bond fission and the formation of free radicals -understand catalytic cracking and thermal cracking in terms of a free radical process -know and understand the mechanism of photochemical chlorination L.O

What is ORGANIC 5 min https://www.youtube.com/watch?v=xCooJNHOSXc Teravalencey Catenation Isomerization

TYPES OF FORMULAE - 1 Fuse School 5 min. MF, EF, Displayed Formula https://www.youtube.com/watch?v=9SX-iWpi98g MOLECULAR FORMULA C4H10 The exact number of atoms of each element present in the molecule EMPIRICAL FORMULA C2H5 The simplest whole number ratio of atoms in the molecule CONDENSED FORMULA CH3CH2CH2CH3 CH3CH(CH3)CH3 STRUCTURAL (DISPLAYED) FORMULA there are two possible ISOMERS of C4H10 structures Isomers (Fuse School) https://www.youtube.com/watch?v=NgzFok_BA_0&t=165s

A systematic name has two main parts. I.U.P.A.C. NOMENCLATURE L.O. Understand and be able to use the IUPAC nomenclature A systematic name has two main parts. Number of carbon atoms in : longest chain side-chains CH3 CH2 CH Prefix C atoms. Alkane meth- 1 methane eth- 2 ethane prop- 3 propane but- 4 butane pent- 5 pentane hex- 6 hexane hept- 7 heptane oct- 8 octane non- 9 nonane dec- 10 decane A prefix derived from the Greek numbering system. Yeah, ok, not the first 4. The ending -ane is the same as they are all alkanes.

Rules for Naming Alkanes (Nomenclature) The numbering starts at the end closest to the branching. The side chains end in yl. —CH3 Methyl 1 —CH2CH3 Ethyl 2 3 4 —CH2CH2CH3 Propyl Methyl

Alkanes - Nomenclature The parent name, the longest continuous chain. The suffix indicates what functional group is present. The prefix tells us the identity, location, and number of substituents attached to the carbon chain.

Alkanes - Nomenclature Also note that if there are two chains of equal length, pick the chain with more substituents.

Alkanes - Nomenclature 1. Find the parent carbon chain and add the suffix. Note that it does not matter if the chain is straight or it bends.

Alkanes - Nomenclature 2. Number the atoms in the carbon chain to give the first substituent the lowest number.

Alkanes - Nomenclature A tie, break it by giving lower number to earliest letter.

Alkanes - Nomenclature Cycloalkanes are named all the SAME way, but the prefix cyclo- immediately precedes the name of the parent. 1. Find the parent cycloalkane.

Alkanes - Nomenclature Keep numbers as LOW as possible

Cyclic Alkanes Cyclopropane, C3H6 Cyclobutane, C4H8 Cyclopentane, C5H10 Cyclohexane, C6H12 Cycloheptane, C7H14 Remember, hydrogens are left out

I.U.P.A.C. NOMENCLATURE CH3 CH2 CH Now this NOTE: 1) If identical side-chains appear more than once, prefix with di, tri, tetra, penta, hexa 2) Numbers are separated from names by a HYPHEN e.g. 2-methylheptane 3) Numbers are separated from numbers by a COMMA e.g. 2,3-dimethylbutane Try this compound 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 CH Now this 2-chloro-3,6-dimethylnonane

How long is the longest chain? 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. CH2 CH3 CH THE ANSWERS ARE ON THE NEXT SLIDE CH2 CH3 CH CH3 CH CH2

Apply the rules and name these alkanes I.U.P.A.C. NOMENCLATURE I.U.P.A.C. NOMENCLATURE Apply the rules and name these alkanes Longest chain = 5 so it is a pentane A CH3, methyl, group is attached to the third carbon from one end... 3-methylpentane CH2 CH3 CH Longest chain = 6 so it is a hexane A CH3, methyl, group is attached to the second carbon from one end... 2-methylhexane CH2 CH3 CH 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 CH3 CH CH2

ALKENES

NAMING ALKENES DOUBLE BONDS Alkanes v Alkenes. (Fuse School) https://www.youtube.com/watch?v=Sfm3eHe57PU&t=22s Length In alkenes the principal chain is not always the longest chain It must contain the double bond the name ends in -ENE Position Count from one end SAME as Before….as with the alkanes. Indicated by the lower numbered carbon atom on one end of the C=C bond 5 4 3 2 1 CH3 CH2 CH=CH CH3 is pent-2-ene (NOT pent-3-ene) Side-chain Similar to alkanes position is based on the number allocated to the double bond WATCH OUT, SIDE CHAIN IN BRACKETS!!! 1 2 3 4 1 2 3 4 CH2 = CH(CH3)CH2CH3 CH2 = CHCH(CH3)CH3 2-methylbut-1-ene 3-methylbut-1-ene

Alkynes - Nomenclature Alkynes are named in the same general way that alkenes are named; just change the suffix to –yne.

Homologous organs

For discussing ethane, ethene, ethyne, propane, propene, propyne C2H2, C2H4, C2H6, C3H4, C3H6, C3H8

Homologous series of alkanes

have similar chemical properties have physical properties that vary in a regular manner as the number of carbon atoms increases because of homologuous series Example: the alkanes

The main features of a homologous series Successive members of a homologous series differ by a – CH2 group Members of a homologous series can be represented by the same general formula Members of a homologous series show a gradation in their physical properties Members of a series have similar chemical properties

Types of Isomerism Isomerism Structural Chain Position Functional Stereo Geometrical Optical

Chain isomerism pentane 2-methylbutane 2,2-dimethylpropane

Position isomerism butan-1-ol butan-2-ol

Position isomerism but-1-ene but-2-ene

Structural Formulas for C4H10O Isomers

Functional isomerism for C2H6O dimethylether ethanol

Functional isomerism C3H6O propanal propanone (acetone)

PHYSICAL PROPERTIES OF ALKANES Boiling point Homologous series increases as they get more carbon atoms in their formula more atoms = greater intermolecular Van der Waals’ forces greater intermolecular force = more energy to separate the molecules greater energy required = higher boiling point Spot the differences CH4 (-161°C) C2H6 (-88°C) C3H8 (-42°C) C4H10 (-0.5°C) difference gets less - mass increases by a smaller percentage Straight chains molecules have greater interaction than branched “The greater the branching, the lower the boiling point” STRUCTURAL ISOMERS OF C5H12 HIGHEST BOILING POINT LOWEST BOILING POINT

Trends in boiling points of members of a homologous series melting point and boiling point increase with more carbon atoms Why? intermolecular forces increase adding a CH2 adds more electrons this increases the Van der Waal’s forces Alkane Formula Boiling Pt./oC methane CH4 -162.0 ethane C2H6 -88.6 propane C3H8 -42.2 butane C4H10 -0.5 Intermolecular forces present & molar mass

STRUCTURAL ISOMERISM - CHAIN 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 straight chain - 11.7°C branched greater branching = lower boiling point

ETHANOL METHOXYMETHANE Physical Properties. HB. No HB STRUCTURAL ISOMERISM – FUNCTIONAL GROUP ALCOHOLS and ETHERS C2H6O and. C2H6O ETHANOL METHOXYMETHANE Physical Properties. HB. No HB Chemical Properties Very reactive. Inert ALDEHYDES and KETONES C3H6O and C3H6O PROPANAL PROPANONE Physical Properties. Polar Polar (similar) Chemical Properties Very reactive. Inert ACIDS and ESTERS C3H6O2. and C3H6O2. PROAPNOIC acid METHYLETHANOATE Physical Properties. HB No HB Chemical Properties Very reactive. Inert

Functional Groups (Fuse Schol) https://www.youtube.com/watch?v=nMTQKBn2Iss&t=140s

-OH -COOH -CHO -C- -O- -C-O -N- -C-NH Alcohols Organic acids Aldehydes Ketones Ethers Esters Amines Amides -OH hydroxyl -COOH carboxyl -CHO carbonyl O -C- -O- O -C-O -N- O -C-NH