Presentation on theme: "8–1 John A. Schreifels Chemistry 212 Chapter 24-1 Chapter 24 Organic Chemistry."— Presentation transcript:
8–1 John A. Schreifels Chemistry 212 Chapter 24-1 Chapter 24 Organic Chemistry
8–2 John A. Schreifels Chemistry 212 Chapter 24-2 Overview Bonding of Carbon Hydrocarbons –Alkanes and Cycloakanes –Alkenes and Alkynes –Aromatic Hydrocarbons –Naming Hydrocarbons Derivatives of Hydrocarbons –Organic compounds containing Oxygen –Organic compounds containing Nitrogen
8–3 John A. Schreifels Chemistry 212 Chapter 24-3 Bonding of Carbon Carbon has 4 valence electrons (2s 2 2p 2 ) needs 4 electrons to fill octet. –sp 3 hydbridization: four bonds to carbon, CH 4 –sp 2 hydridization: three bonds to carbon; two single bonds and 1 double bond. CH 2 =CH 2 –sp hybridization: two bonds to carbon; 1 single bond and 1 triple bond, CH≡CH Carbon can bond to other carbon atoms to form very extensive and complicated molecular systems.
8–4 John A. Schreifels Chemistry 212 Chapter 24-4 Hydrocarbons Compounds containing only carbon and hydrogen –Saturated hydrocarbons contain only single bonds and are sp 3 hybridized. (aliphatic) –Unsaturated hydrocarbons contain at least one double or triple bond. (aliphatic) –Aromatic hydrocarbons: very stable unsaturated compounds such as benzene: C 6 H 6. A = propane B = cyclohexane C = acetylene D = benzene
8–5 John A. Schreifels Chemistry 212 Chapter 24-5 Alkanes and Cycloalkanes Alkanes = acyclic (not cyclic) saturated hydrocarbons Cycloalkanes = cyclic saturated hydrocarbons. Molecular formula: gives number and kind of atoms Structural formula: gives how bonding between different atoms.
8–6 John A. Schreifels Chemistry 212 Chapter 24-6 Alkanes Often called Paraffins General formula C n H 2n+2 where n = 1 … E.g. n = 1 CH 4 ; n = 2 C 2 H 6, etc. Straight chain (normal) alkanes = carbon atoms connected to each other to form a chain of carbon atoms:
8–7 John A. Schreifels Chemistry 212 Chapter 24-7 Alkanes: Homologous Series Homologous series: series of compounds which differ by fixed number of atoms (e.g. for alkanes they differ only by –CH 2 - group. The names and physical properties of the first ten alkanes are shown on Fig. 24.1Fig. 24.1 Physical properties of homologous series vary in a predictable manner. –MP and BP increase with number of carbons (Molecular Mass).
8–8 John A. Schreifels Chemistry 212 Chapter 24-8 Branched Chain Alkanes; Constitutional Isomers Branched chain alkanes such as isobutane are hydrocarbons with carbons not always arranged in a straight chain. Butane and Isobutane have the same molecular formula, but different structure. Constitutional (Structural) Isomer – compounds with the same molecular formula but different structural formula. Butane and Isobutane (2-methyl propane) are structural Isomers.
8–9 John A. Schreifels Chemistry 212 Chapter 24-9 Cycloalkanes Hydrocarbons where the carbons form a ring or cyclic structure; General formula: C n H 2n.
8–10 John A. Schreifels Chemistry 212 Chapter 24-10 Alkenes and Alkynes Unsaturated (contains one or more double or triple bonds) hydrocarbons Double and triple bonds are more reactive than single bonds which makes unsaturated hydrocarbons more reactive than saturated hydrocarbons. Alkenes (C n H 2n ) are also called olefins and contain carbon – carbon double bonds. –All atoms around the double bond are in a plane –Molecules containing a double bond can have geometric isomer when there are the same groups on each side of the molecule but they are located in slightly different positions. E.g. 2 - butene exists as cis and trans isomers cis-2-butene trans-2-butene
8–11 John A. Schreifels Chemistry 212 Chapter 24-11 Alkenes: Addition & Oxidation Reactions Oxidation: Alkenes can be partially oxidized by permanganate to produce a brown precipitate called manganese dioxide: 3C 2 H 5 CH=CH 2 + 2MnO 4 (aq) + 4H 2 O 3C 2 H 5 CHOHCH 2 OH + 2MnO 2 (s) + 2OH (aq) Addition: Reactant is added to the two carbons that form the multiple bond: H 2 C=CH 2 + Br 2 H 2 CBrCH 2 Br –Addition of H 2 (called hydrogenation) gives a hydrocarbon H 2 C=CH 2 + H 2 CH 3 CH 3 –Unsymmetrical molecules (e.g. HCl, HBr) can add in two ways: Markownikoff’s Rule: addition of unsymmetrical reagent gives product in which the hydrogen adds to the carbon with the most hydrogens attached to it => the second product is the dominant one.
8–12 John A. Schreifels Chemistry 212 Chapter 24-12 Alkynes Alkynes are compounds containing triple bonds. Addition reactions of alkynes behave similarly to alkenes (Markownikoff’s rule):
8–13 John A. Schreifels Chemistry 212 Chapter 24-13 Aromatic Hydrocarbons A cyclic compound containing several degrees of unsaturation (double bonds). Aromatic compounds have resonance hybrids and thus are more stable than normal unsaturated compounds. E.g. Cl 2 does not readily add to an aromatic double bond, but reacts quite rapidly with normal unsaturated compounds.
8–14 John A. Schreifels Chemistry 212 Chapter 24-14 Reactions on Aromatic Rings: Substitution Aromatic Substitution reaction – Aromatic compound loses a hydrogen atom and another atom or group takes its place. It is possible for substitution to occur in more than one place on the ring.
8–15 John A. Schreifels Chemistry 212 Chapter 24-15 Naming Alkanes Straight-Chain Alkanes (see Table 24.1)Table 24.1 Branched chain has substituents on the molecule; does not form a single simple straight chain. Name branched-chain alkanes using the format: Prefix-Parent-Suffix –Prefix specifies position and number of various substituents –Parent tells how many carbons atoms are present on the longest continuous chain. –Suffix tells to what family the molecule belongs (alkanes: -ane; alkenes: -ene, etc) Branched Chain Alkane
8–16 John A. Schreifels Chemistry 212 Chapter 24-16 Naming Alkanes Determine the longest chain; use the name of that chain as the parent name; be careful to look for the longest chain. –The name of the chain below would be hexane not butane. Number carbons starting from end nearest substituent. Name and locate each substituent group (-ane becomes –yl ending) With two or more substituents list them in alphabetical order; use di-, tri- etc. for identical substituents. 3-methylhexane 3-ethyl-2,3dimethylpentane
8–17 John A. Schreifels Chemistry 212 Chapter 24-17 Functional Groups Organic compounds often contain elements other than C, H that increase their reactivity. Functional Groups are the reactive portions of the molecule that undergo predictable reactions depending upon the functional group.
8–18 John A. Schreifels Chemistry 212 Chapter 24-18 List of Organic Functional Groups
8–19 John A. Schreifels Chemistry 212 Chapter 24-19 Names and Properties of the Straight Chain Alkanes Return to Slide 7 Return to Slide 15