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ORGANIC CHEMISTRY Chapter 20 Organic • Comes from the word “organism” • Originally thought that carbon compounds could only be synthesized by living organisms • Not so – German scientist synthesized urea – a carbon compound found in urine in 1828 Carbon Bonding • Because carbon bonds readily with H, N, O, S, and halogens, as well as itself, there are millions of carbon compounds. • Carbon compounds are considered organic EXCEPT for – carbon dioxide, – carbides, and – carbonates. Hydrocarbons • Simplest organic compounds • Contain only hydrogen and carbon in long strings or chains • Their carbon-carbon covalent bonds are single • Saturated – has the maximum number of hydrogens - alkanes When a carbon atom has 4 atoms bound to it, these atoms form a tetrahedral shape. Representing Alkanes • Chemical formulas - generic alkane formula is CnH2n+2, ex. CH4, C2H6, C3H__ • Structural formulas – show all C’s and H’s • Condensed structural formulas – C’s with # of H’s attached. ex. CH3 CH2 CH2 CH3 • If there is more than one way to correctly represent an alkane it has structural isomerism – the different structures are called isomers Naming Straight Chain Alkanes all carbon – carbon bonds are single bonds • Count the number of carbons and use appropriate prefix with “ane” ending. • meth -1, • eth -2, • prop - 3, • but - 4, • pent- 5, • hex - 6, • hept - 7, • • • • • • • • oct- 8, non - 9, dec- 10 Ex. Name CH4 1 carbon, so methane Name C2H6 2 carbons, so ethane Alkanes: see table 20.1 on page 704 Alkenes have a double carbon-carbon bond • generic alkene formula is CnH2n • Unsaturated – because of the double bond, has less than maximum number of hydrogens • Count the number of carbons and use appropriate prefix with “ene” ending. • As necessary, number the carbons so as to identify the location of the double bond on the lowest numbered carbon. Alkynes have a triple carbon-carbon bond • generic alkyne formula is CnH2n-2 • Unsaturated – because of the triple bond, has less than maximum number of hydrogens • Count the number of carbons and use appropriate prefix with “yne” ending. • As necessary, number the carbons so as to identify the location of the triple bond on the lowest numbered carbon. • Not common in nature Substituent groups • A group that is substituted for a hydrogen • Named by the number of carbons in the group with a “yl” ending • Ex. If a hydrogen is replaced by a CH3 it is a methyl substituent. • What would the substituent be if CH2CH3 replaced a hydrogen? • See table 20.2 on page 709 Naming Alkanes with Substituent(s) page 710 (aka as branched chains) • Find the longest continuous chain of carbon atoms (may not be “straight”) – this is the parent chain and determines the base alkane name • Number the carbons in the chain so that the substituent group (alkyl group – carbon(s) and hydrogen) is on the lowest # carbon • Using the appropriate name for each alkyl group, identify its place on the parent chain with a number. Naming Alkanes with Substituent(s) con’t • When a given type of alkyl group occurs more than once, attach the appropriate prefix (di, tri, etc.) to the alkyl name. • If there is more than one type of alkyl group, they are listed in alphabetical order, disregarding any prefix. • Commas separate numbers. • Dashes separate numbers from letters. Substituent groups with alkenes and alkynes • Same as alkanes with 2 differences • 1. parent chain is always the longest chain containing the double or triple bond (even though it may not be the longest possible chain) • 2. position of double or triple bond (not branches) determines how the chain is numbered Homework • Practice Problem 20.1 page 703 • practice 20.4 (page 711) and 20.5 (page 714) • Page 717, #1,3,4, (#4 name them too), 6, 8 • Page 719 practice problem 20.6 Functional Groups • Table 20.6 page 727 • An atom or group of atoms in a hydrocarbon derivative that contains elements in addition to carbon and hydrogen. Halocarbons • A halogen replaces one of the hydrogens in a carbon chain. • If necessary, number the carbons and identify the location of the halogen(s) • Ex. chloromethane • 1,2-dichloromethane • 1,1-dichloromethane Alcohols • Most common • Have -OH group on carbon chain replacing a hydrogen Aldehydes and Ketones • Aldehydes have a carbonyl group (C=O) at the end of a carbon chain • To name, replace final “e” of parent chain with “al” Will always be on # 1 carbon Ex. ethanal • Ketones have a carbonyl group (C=O) in the midst of a carbon chain • To name, number carbons so that carbon in carbonyl group has smallest number, then replace final “e” of parent chain with “one”. Identify position of carbonyl group with #. Ex. 2-pentanone Carboxylic acids • Have a carboxyl group (-COOH (one of the oxygens is doubled bonded to the carbon)) • Name by dropping the final “e” on the parent chain (longest chain with COOH group) and adding “oic acid” • Ex. HCOOH methanoic acid type Alkanes Alkenes Alkynes Substituent groups Halocarbons Alcohols Aldehydes Ketones Carboxylic acids Special feature Naming HW – due Thursday 5/13 • P. 735 #20.9 • P 741 #2 • P 746 #48, 49, 50 a-d; 51 b,c,e; 54 a,d; 55 a,d,e