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Chapter 23: Organic Chemistry Key topics: Nomenclature Functional groups Drawing skeletal structures Organic Chemistry o study of carbon-containing compounds o originally: compounds produced by living organisms o now: includes man-made compounds such as plastics Why Carbon is Different electron configuration: [He]2s22p2 o effectively prohibits ion formation (energetically VERY unfavorable to gain/lose 4 e–) o fills octet by sharing e– Small atomic radius, n = 2 valence shell (no 2d orbitals) o short, strong bonds o good p orbital overlap to give π bonds o no 2d orbitals imparts stability (Si more reactive) o catenation to form chains and rings containing single, double and triple bonds ethane: stable in water and air disilane: breaks down in water and spontaneously combusts in air Classes of Organic Compounds Variety comes from o carbon forming chains by bonding to itself o presence of elements other than C and H o Functional groups – a group of atoms that determines many of a molecule’s properties o multiple bonds Alkanes: • contain C atoms connected by single bonds, and H atoms connected to C with single bonds Low density; totally insoluble in water • Naming: 1. Identify the longest continuous C chain to get the parent name (root + “ane”) 2. Number the C’s in the continuous chain, beginning at the end closest to the substituent (branch point) 3. Identify the substituent and use a number and a prefix to specify location and identity, respectively # of Carbons 1 2 3 4 5 6 7 8 9 10 Root name Meth– Eth– Prop– But– Pent– Hex– Hept– Oct– Non– Dec– • alkyl group: alkane minus one H -- substituent Name: H H H C H H H H H H H C H H H H H H H C C C C C C H H C C C C C C H H H H H H H C H H H H H H H C H H H 3,3-dimethylhexane --------------------------------------------- --------------------------------------------- --------------------------------------------- Other Functional Groups: • functional groups determine chemistry that compound will undergo (electrostatic maps shown below) Alcohols: • contains –OH group (hydroxyl group) Methanol, ethanol, and propyl alcohol are miscible with water • naming: 1. Identify the longest chain that includes the –OH group 2. Change the –e ending to -ol 3. Number to give the –OH the lowest number 4. When the chain also contains an alkyl substituent, give the –OH the lowest number --------------------------------------------- --------------------------------------------Carboxylic Acids: • contains –COOH (carboxy) group polar; form strong hydrogen bonds with each other and water • naming: 1. Identify the longest chain that includes the carboxyl group 2. Change the –e ending to –oic acid 3. Number starting with the carbonyl (C=O) carbon 4. Use numbers and prefixes to indicate the position and identity of any substituents Esters: • contain –COO– group (between two other non-H groups) polar but cannot form strong hydrogen bonds • naming: -- Name as derivative of carboxylic acid by replacing the –ic acid ending with –ate st -- 1 part of name specifies the substituent that replaces the ionizable hydrogen of the corresponding acid Aldehydes: • contains –COH (carbonyl group) – at end of chain polar but cannot form strong hydrogen bonds with each other; however can form strong hydrogen bonds with water. • naming: 1. Identify the longest chain that includes the carbonyl group 2. Change the –e ending to -al 3. Number starting with the carbonyl (C=O) carbon 4. Use numbers and prefixes to indicate the position and identity of any substituents Ketones: • contains –CO– (carbonyl group) -- between two other groups polar but cannot form strong hydrogen bonds with each other; however can form strong hydrogen bonds with water. • naming: 1. Identify the longest chain that includes the carbonyl group 2. Change the –e ending to -one 3. Number to give the carbonyl group the lowest possible number 4. Use numbers and prefixes to indicate the position and identity of any substituents --------------------------------------------CH3 O CH3 CH CH2 C OH --------------------------------------------O CH3 CH2 CH2 C CH3 --------------------------------------------- Primary Amines: • contains –NH2 group moderately polar; can form strong hydrogen bonds to each other and to water • naming: 1. Identify the longest chain that includes the –NH2 group 2. Change the –e ending to -amine 3. Number starting with the carbon to which the –NH2 group is bonded 4. Use numbers and prefixes to indicate the position and identity of any substituents Primary Amides: • contains –CONH2 group (e.g. peptides) can form strong hydrogen bonds to each other; therefore amides have high melting and boiling points • naming: 1. Can be named as derivatives of carboxylic acids -- Or, by replacing the –e ending with –amide Compounds with More than One Substituent: • Prefixes of di, tri, tetra, penta and so forth are used to denote the number of substituents • Substituent names are alphabetized • Numbers are used to indicate position of the alphabetized substituents • Prefixes are not counted when alphabetizing Representing Organic Molecules: • large numbers of ways to organize atoms in an organic molecules: e.g. C5OHx • Condensed structural formula (Condensed Structure): shows the same information as a structural formula but in condensed form octane: C8H18 molecular formula CH3(CH2)6CH3 condensed structural formula -- branches indicated using parentheses 2-methylheptane C8H18 Molecular formula CH3CH(CH3)(CH2)4CH3 condensed structural formula • Kekulé structures: similar to Lewis structure but without showing lone pairs • Skeletal Structures: Consist of straight lines that represent carbon-carbon bonds. -- Heteroatoms (atoms other than C or H) shown explicitly