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Organic Chemistry: Introduction IB Topic 10 10.1 Introduction 10.1.1 Describe the features of a homologous series. 10.1.2 Predict and explain the trends in boiling points of members of a homologous series. 10.1.3 Distinguish between empirical, molecular and structural formulas. 10.1.4 Describe structural isomers as compounds with the same molecular formula but with different arrangement of atoms. 10.1.5 Deduce structural formulas for the isomers of noncyclic alkanes up to C6. 10.1.6 Apply IUPAC rules for naming the isomers of the non-cyclic alkanes up to C6. What is organic chemistry? Organic Chemistry The study of carbon, the compounds it makes and the reactions it undergoes. Over 16 million carbon-containing compounds are known. What is organic chemistry? Carbon Carbon can form multiple bonds to itself and with atoms of other elements. Carbon can only make four bonds since it has 4 valence electrons and most often bonds to H, O, N and S. Because the C-C single bond (348 kJ mol1) and the C-H bond (412 kJ mol-1) are strong, carbon compounds are stable. Carbon can form chains and rings. What is organic chemistry? Hydrocarbons Hydrocarbons are organic compounds that only contain carbon and hydrogen Types of hydrocarbons include Alkanes Alkenes Alkynes Aromatic 10.1.1 Describe the features of a homologous series. A homologous series is a series of related compounds that have the same functional group. Homologous compounds… Differ from each other by a – CH2 – unit (methylene group) Can all be represented by a general formula Have similar chemical properties Have physical properties that vary in a regular manner as the number of carbon atoms present increases #C Prefix Alkane (ane) Alkene (ene) CnH2n+2 CnH2n 1 meth CH4 methane 2 eth C2H6 ethane 3 prop 4 but 5 pent 6 hex C2H4 ethene 10.1.2 Predict and explain the trends in boiling points of members of a homologous series. What is the trend? Why? Alkane Formula Boiling Pt./oC methane CH4 -162.0 ethane C2H6 -88.6 propane C3H8 -42.2 butane C4H10 -0.5 10.1.2 Predict and explain the trends in boiling points of members of a homologous series. Intermolecular forces present Simple alkanes, alkenes, alkynes → van der Waals’ forces (nonpolar) → lower b.p. Aldehydes, ketones, esters & presence of halogens (polar) → dipole: dipole forces → slightly higher b.p. Alcohol, carboxylic acid & amine → hydrogen bonding (w/ O, N, F) → even higher b.p. 10.1.2 Predict and explain the trends in boiling points of members of a homologous series. 10.1.3 Distinguish between empirical, molecular and structural formulas. Empirical Formula: Smallest whole number ratio of atoms in a formula Molecular Formula: Formula showing the actual numbers of atoms Molecular Formula Empirical Formula CH4 CH4 C2H6 CH3 C6H12O6 C4H8 C8H16 10.1.3 Distinguish between empirical, molecular and structural formulas. Structural Formula Bond angles are drawn as though 90o. The true shape around C with 4 single bonds is tetrahedral and the angle is 109.5o. Show every atom and every bond. Can use condensed structural formulas. Hexane: CH3CH2CH2CH2CH2CH3 (condensed s.f.) M.F. = C6H14 E.F. = C3H7 10.1.3 Distinguish between empirical, molecular and structural formulas. 10.1.4 Describe structural isomers as compounds with the same molecular formula but with different arrangement of atoms. Isomers: different compounds that have the same molecular formula Structural isomers: an isomer in which the atoms are joined in a different order so that they have different structural formulae 10.1.4 Describe structural isomers as compounds with the same molecular formula but with different arrangement of atoms. 10.1.5 Deduce structural formulas for the isomers of non-cyclic alkanes up to C6. If there is a branch off of the main chain, put that formula in parentheses CH3CH(CH3)CH3 CH3CH2CH2CH3 10.1.5 Deduce structural formulas for the isomers of non-cyclic alkanes up to C6. Draw out and write the structural formulas for all isomers that can be formed by: CH4 C2H6 C3H8 C4H10 C5H12 C6H14 10.1.6 Apply IUPAC rules for naming the isomers of the non-cyclic alkanes up to C6. 1. 2. 3. 4. Determine the longest carbon chain Use the prefix (next slide) to denote the number carbons in the chain Use the suffix “-ane” to indicate that the substance is an alkane If the chain is branched, the name of the side chain will be written before the main chain and will end with “–yl” 10.1.6 Apply IUPAC rules for naming the isomers of the non-cyclic alkanes up to C6. Methylpropane Methylbutane Dimethylbutane 10.1.6 Apply IUPAC rules for naming the isomers of the non-cyclic alkanes up to C6. 1 Meth- 6 Hex- 2 Eth- 7 Hept- 3 Prop- 8 Oct- 4 But- 9 Non- 5 Pent- 10 Dec- 10.1.6 Apply IUPAC rules for naming the isomers of the non-cyclic alkanes up to C6. For chains longer than 4 carbons with side chains: 5. Number the carbons in the chain consecutively, starting at the end nearest side chains. 6. Designate the location of each substituent group by an appropriate number and name. And with 2 or more side chains: 5. Use prefixes di-, tri-, tetra-, to indicate when there are multiple side chains of the same type. 6. Use commas to separate numbers and hyphens to separate numbers or letters. 7. Name the side chains in alphabetical order. 10.1 Introduction, cont. 10.1.7 Deduce structural formulas for the isomers of the straightchain alkenes up to C6. 10.1.8 Apply IUPAC rules for naming the isomers of the straight-chain alkenes up to C6. 10.1.9 Deduce structural formulas for compounds containing up to six carbon atoms with one of the following functional groups: alcohol, aldehyde, ketone, carboxylic acid and halide. 10.1.10 Apply IUPAC rules for naming compounds containing up to six carbon atoms with one of the following functional groups: alcohol, aldehyde, ketone, carboxylic acid and halide. 10.1.11 Identify the following functional groups when present in structural formulas: amino (NH2), benzene ring ( ) and esters (RCOOR). 10.1.12 Identify primary, secondary and tertiary carbon atoms in alcohols and halogenoalkanes. 10.1.13 Discuss the volatility and solubility in water of compounds containing the functional groups listed in 10.1.9. 10.1.7 Deduce structural formulas for the isomers of the straight-chain alkenes up to C6. Remember that structural formulas show the relative location of atoms around each carbon Hexane: CH3CH2CH2CH2CH2CH3 (condensed s.f.) M.F. = C6H14 Determine the molecular formulas for the alkenes below. Draw out and write the structural formulas for all isomers that can be formed by each. C2H4 C3H? C4H? C5H? C6H? 10.1.8 Apply IUPAC rules for naming the isomers of the straight-chain alkenes up to C6. Alkenes have one (or more) carbon to carbon double bonds Suffix changes to “-ene” When there are 4 or more carbon atoms in a chain, the location of the double bond is indicated by a number. Begin counting the carbons closest to the end with the C=C bond Numbering the location of the double bond(s) takes precedence over the location of side chains 1-butene 2-butene methylpropene 25 10.1.9 Deduce structural formulas for compounds containing up to six carbon atoms with one of the following functional groups: alcohol, aldehyde, ketone, carboxylic acid and halide. Functional group = a group of atoms that defines the structure of a family and determines its properties 10.1.9 Deduce structural formulas for compounds containing up to six carbon atoms with one of the following functional groups: alcohol, aldehyde, ketone, carboxylic acid and halide. Functional Group Alcohol Aldehyde Formula -OH Structural Formula -O–H -COH (on the O end of a chain) - C – H Ketone - CO – (not on O the end) -C– Carboxylic Acid -COOH O -C–O–H Functional Groups 10.1.10 Apply IUPAC rules for naming compounds containing up to six carbon atoms with one of the following functional groups: alcohol, aldehyde, ketone, carboxylic acid and halide. Functional Group Formula Alcohol -OH Suffix (or Prefix) -ol Aldehyde -COH -al Ketone - CO - -one Carboxylic Acid Halide -COOH -oic acid -Br, -Cl, -F, -I Bromo-, 10.1.11 Identify the following functional groups when present in structural formulas: amino (NH2), benzene ring ( ) and esters (RCOOR). A few more groups: Functional Formula Group Amine - NH2 Ester Benzene O R–C–O–R Ethyl ethanoate 10.1.11 Identify the following functional groups when present in structural formulas: amino (NH2), benzene ring ( ) and esters (RCOOR). Esters are used for fragrances and flavoring agents since one of their major properties is smell Benzene is in a family known as the aromatic hydrocarbons… because they smell 10.1.12 Identify primary, secondary and tertiary carbon atoms in alcohols and halogenoalkanes. With reference to the carbon that is directly bonded to an alcohol group or a halogen: Primary = carbon atom is only bonded to one other carbon Secondary = carbon atom is bonded to two other carbons Tertiary = carbon atom is bonded to three other carbons 10.1.13 Discuss the volatility and solubility in water of compounds containing the functional groups listed in 10.1.9. Volatility: how easily a substance turns into a gas The weaker the intermolecular force, the more volatile it is So, is a nonpolar or polar substance more volatile? Solubility: a solute’s ability to dissolve in a polar solvent (water) The more polar a substance is, the more soluble it is 10.1.13 Discuss the volatility and solubility in water of compounds containing the functional groups listed in 10.1.9. Volatility: vdW › d-d › H alkane › halogenoalkane › aldehyde › ketone › amine › alcohol › carboxylic acid Solubility: If the functional group is soluble (hydrogen bonded), it will be more soluble Solubility decreases as chain length increases Smaller alcohols, aldehydes, ketones & carboxylic acids are typically soluble Halogenoalkanes are NOT soluble since they don’t form hydrogen bonds