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ORGANIC CHEMISTRY Any molecule that contains the element CARBON “Natural” Products: Poison Ivy Snake Venom Tobacco Poison Hemlock "Organic" does not mean "natural." Manmade Organic Substances Organic Chemistry Hydrocarbons ONLY Carbon and Hydrogen Alkene Alkyne other Substituded Hydrocarbons Alkane Ring :Aromatic (Benzene) HYDROCARBONS: “alk”- Only contain Hydrogen and Carbon Type of bond Between CARBONS determines the family Alkane = all single bond Alkene = double bond Alkyne = triple bond Hydrocarbons 6 Alkanes: general formula CnH2n+2 •CH4 = methane •C2H6 = ethane •C3H8 = propane •C4H10 = butane •C5H12 = pentane HYDROCARBONS: Naming ALKANES: name and formula Structural Formulas Alkanes are written with structural formulas that are • expanded to show each bond • condensed to show each carbon atom and the attached hydrogen atoms 10 Basic Chemistry Copyright © 2011 Pearson Education, Inc. Draw the condensed structural formula for heptane. Heptane, an alkane, has seven carbon atoms in its carbon chain. CH3─CH2─CH2─CH2─CH2─CH2─CH3 11 Basic Chemistry Copyright © 2011 Pearson Education, Inc. Name each of the following: A. CH3─CH2─CH2─CH3 four carbon atoms; butane B. CH3─CH2─CH2─CH2─CH2─CH2─CH2─CH3 eight carbon atoms; octane 12 Basic Chemistry Copyright © 2011 Pearson Education, Inc. 22.1 Hydrocarbons > Alkanes Straight-Chain Alkanes • For the straight-chain alkanes with one to four carbon atoms, the official names and the common names are the same. • For the chains longer than 4, the prefixes are pent- for 5, hex- for 6, hept- for 7, oct- for 8, non- for 9, and dec- for 10. 13 Straight-Chain Alkanes Name Formula Methane CH4 Ethane C2H6 Propane C4H8 Butane C4H10 Pentane C5H12 Hexane C6H14 Heptane C7H16 Octane C8H18 Nonane C9H20 Decane C10H22 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Isomers of Butane straight chain Isomers • have the same molecular formula • have different atomic structure branched 14 Basic Chemistry Copyright © 2011 Pearson Education, Inc. 22.1 Hydrocarbons > Alkanes Branched-Chain Alkanes • The longest continuous carbon chain of a branched-chain hydrocarbon is called the parent alkane. • All other carbon atoms or groups of carbon atoms are regarded as substituents. • Atoms such as halogens, oxygen, and nitrogen can also be substituents. 15 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 22.1 Hydrocarbons > Alkanes Branched-Chain Alkanes • A hydrocarbon substituent that is derived from an alkane is called an alkyl group. • You can think of any alkyl group as just an alkane with one of the hydrogens removed. • Alkyl groups are named by removing the -ane ending from the parent hydrocarbon name and adding -yl. 16 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 22.1 Hydrocarbons > Alkanes Branched-Chain Alkanes • The three smallest alkyl groups are • the methyl group (–CH3) • the ethyl group (–CH2CH3) • the propyl group (–CH2CH2CH3) • When a substituent alkyl group is attached to a straight-chain hydrocarbon, branches are formed. • An alkane with one or more alkyl groups is called a branched-chain alkane. 17 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 22.1 Hydrocarbons > Alkanes Branched-Chain Alkanes Examples of primary, secondary, tertiary, and quaternary carbons are labeled in the structural formulas below. 18 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 22.1 Hydrocarbons > Alkanes Branched-Chain Alkanes The compound with the following structural formula can be used as an example. 19 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 22.1 Hydrocarbons > Alkanes Branched-Chain Alkanes 1. Find the longest continuous chain of carbons in the molecule. This chain is considered the parent hydrocarbon. • The longest chain is highlighted in the example. It contains seven carbon atoms. So, the parent hydrocarbon is heptane. 20 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 22.1 Hydrocarbons > Alkanes Branched-Chain Alkanes 2. Number the carbons in the main chain in sequence. To do this, start at the end that will give the substituent groups attached to the chain the smallest numbers. • Numbering the chain from right to left gives the substituents the lowest numbers (2, 3, and 4). 21 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 22.1 Hydrocarbons > Alkanes Branched-Chain Alkanes 3. Add numbers to the names of the substituent groups to identify their positions on the chain. These numbers become prefixes to the name of the substituent group. • The substituents and positions are 2-methyl, 3-methyl, and 4-ethyl. 22 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 22.1 Hydrocarbons > Alkanes Branched-Chain Alkanes 4. Use prefixes to indicate the appearance of the same group more than once in the structural formula. Common prefixes are di- (twice), tri(three times), and tetra- (four times). • The two methyl groups are combined as 2,3dimethyl in the name. 23 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 22.1 Hydrocarbons > Alkanes Branched-Chain Alkanes 5. List the names of alkyl substituents in alphabetical order. For purposes of alphabetizing, ignore the prefixes di-, tri-, and so on. • The 4-ethyl group is listed first, followed by the 2,3-dimethyl. 24 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 22.1 Hydrocarbons > Alkanes Branched-Chain Alkanes 6. Combine all the parts and use proper punctuation. Write the entire name without any spaces. Use commas to separate numbers, and use hyphens to separate numbers and words. • The correct name of the compound is 4ethyl-2,3-dimethylheptane. 25 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Naming Alkanes 26 Basic Chemistry Copyright © 2011 Pearson Education, Inc. Give the IUPAC name of the Alkane CH3 CH3 CH3─CH─CH─CH2─CH2─CH3 1 2 3 4 5 6 STEP 1 Write the alkane name of the longest continuous chain of carbon atoms. hexane STEP 2 Number the carbon atoms starting from the end nearer a substituent. 27 Basic Chemistry Copyright © 2011 Pearson Education, Inc. Example of Naming an Alkane (continued) STEP 3 Give the location and name of each substituent as a prefix to the alkane name. CH3 CH3 methyl groups on carbons 2 and 3 CH3─CH─CH─CH2─CH2─CH3 1 2 3 4 5 6 2,3-dimethylhexane 28 Basic Chemistry Copyright © 2011 Pearson Education, Inc. Give the IUPAC name of CH3 CH3─CH2─CH─CH─CH3 5 4 3 2 1 STEP 1 Write the alkane name of the longest continuous chain of carbon atoms. pentane STEP 2 Number the carbon atoms starting from the end nearer a substituent. 29 Basic Chemistry Copyright © 2011 Pearson Education, Inc. Solution (continued) STEP 3 Give the location and name of each substituent as a prefix to the alkane name. methyl on carbon 3 CH3 CH3─CH2─CH─CH─CH3 5 4 3 2 1 3-methylpentane 30 Basic Chemistry Copyright © 2011 Pearson Education, Inc. Give the IUPAC name for the methyl on CH following carbon 3 3 | CH3─CH2─CH─CH2─C─CH2─CH3 7 6 5 4 3 2 1 STEP 1 Write the alkane name of the longest continuous chain of carbon atoms. heptane STEP 2 Number the carbon atoms starting from the end nearer a substituent. STEP 3 Give the location and name of each substituent as a prefix to the alkane name. 31 Basic Chemistry 3-methylheptane Copyright © 2011 Pearson Education, Inc. Drawing Alkane Formulas 32 Basic Chemistry Copyright © 2011 Pearson Education, Inc. Draw the condensed structural formula for 2-methylbutane STEP 1 Draw the main chain of carbon atoms. For butane, there are four carbon atoms in the chain. C─C─C─C STEP 2 Number the chain and place the substituents on the carbons indicated by the numbers. CH3 C─C─C─C 1 2 3 4 STEP 3 Add the correct number of hydrogen atoms to give four bonds to each C atom. 33 CH3 CH3─CH─CH2─CH3 Basic Chemistry Copyright © 2011 Pearson Education, Inc. Cyclic Hydrocarbons Just as straight-chain and branchedchain alkanes can be either saturated or unsaturated, so can cyclic hydrocarbons. A cyclic hydrocarbon that contains only single bonds, and is therefore saturated is called a cycloalkane. Basic Chemistry © Pearson Copyright © 2011 Pearson Education, Copyright Inc. Education, Inc., or its affiliates. All Rights Reserved. A compound that contains a hydrocarbon ring is called a cyclic hydrocarbon. • Many molecules found in nature contain cyclic hydrocarbons. • Rings with five and six carbons are the most abundant. Basic Chemistry © Pearson Copyright © 2011 Pearson Education, Copyright Inc. Education, Inc., or its affiliates. All Rights Reserved. Cyclic Hydrocarbons To determine the IUPAC name of a cycloalkane, first count the number of carbons in the ring and assign the corresponding alkane name. Then simply add the prefix cyclo- to the alkane name. Name: cyclopropane Basic Chemistry Copyright © Pearson Education, Inc., or © its2011 Pearson Education, Inc. Copyright affiliates. All Rights Reserved. Alkenes: Compounds with C=C Double Bonds 37 Alkenes: general formula CnH2n 3 4 CH2CH3 H H 1 C 1 C 2 C H H 1-butene 3 CH3 H 1 H3C 2 C 4 CH3 2 C CH3 2-methylpropene (isobutene) H 4 CH3 H 3 C 2 C H cis-2-butene 1 H3 C 3 C H trans-2-butene 38 Alkynes • Alkynes have carbon-carbon triple bonds. C2H2: name = ethyne FAMILIES OF HYDROCARBONS: ALKANE, ALKENE, ALKYNE FAMILIES OF HYDROCARBONS: ALKANE, ALKENE, ALKYNE Unsaturated Compounds: Alkenes and Alkynes • have fewer hydrogen atoms attached to the carbon chain than alkanes • are alkenes with C=C double bonds • are alkynes with triple C≡C bonds 41 Basic Chemistry Copyright © 2011 Pearson Education, Inc. Saturated vs Unsaturated Saturated: all SINGLE BONDS Alkanes Unsaturated: double and/or triple bond(s) present. Alkenes Alkynes Naming Alkenes and Alkynes 43 Basic Chemistry Copyright © 2011 Pearson Education, Inc. 22.2 Unsaturated Hydrocarbons > Alkenes • The chain is numbered so that the carbon atoms of the double bond have the lowest possible numbers. • Substituents on the chain are named and numbered in the same way they are for alkanes. 44 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Naming Alkenes and Alkynes 45 Basic Chemistry Copyright © 2011 Pearson Education, Inc. Write the IUPAC name for the following CH 3 | CH3─CH=C─CH3 4 3 2 1 STEP 1 Name the longest carbon chain that contains a double or triple bond. butene STEP 2 Number the carbon chain starting from the end nearer the double or triple bond. STEP 3 Give the location and name of each substituent as a prefix 46 Basic Chemistry 2-methyl-2-butene Copyright © 2011 Pearson Education, Inc. Write the IUPAC name for the following CH3─CH─CC─CH3 5 4 3 2 1 STEP 1 Name the longest carbon chain that contains a double or triple bond. pentyne STEP 2 Number the carbon chain starting from the end nearer the double or triple bond. STEP 3 Give the location and name of each substituent as a prefix 2-pentyne 47 Basic Chemistry Copyright © 2011 Pearson Education, Inc. Draw the condensed structural formula for 2-methyl-3-hexyne. STEP 1 Draw the main chain of carbon atoms. For 3-hexyne, there are six carbon atoms in the chain, with a triple bond between carbons 3 and 4, C─C─C≡C─C─C STEP 2 Number the chain and place the substituents on the carbons indicated by the numbers. CH3 C─C─C≡C─C─C 1 48 Basic Chemistry 2 3 4 5 6 Copyright © 2011 Pearson Education, Inc. Solution (continued) STEP 3 Add the correct number of hydrogen atoms to give four bonds to each C atom. CH3 CH3─CH─C≡C─CH2─CH3 1 2 3 4 5 6 2-methyl-3-hexyne 49 Basic Chemistry Copyright © 2011 Pearson Education, Inc. Special HYDROCARBONS bond Between CARBONS = family Alkane = all single bond Alkene = double bond Alkyne = triple bond AROMATIC Hydrocarbons: contain benzene molecule 22.4 Hydrocarbon Rings> Aromatic Hydrocarbons Any compound not classified as an aromatic compound is an aliphatic compound. Alkanes, alkenes, alkynes, and cycloalkanes are aliphatic compounds. The properties of aromatic compounds are quite different from those of aliphatic compounds. 51 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 22.4 Hydrocarbon Rings> Aromatic Hydrocarbons • An aromatic compound, or arene, is now defined as an organic compound that contains a benzene ring or other ring in which the bonding is like that of benzene. 52 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Aromatic Hydrocarbons Benzene is the simplest aromatic compound 53 Basic Chemistry Copyright © 2011 Pearson Education, Inc. 22.4 Hydrocarbon The StructureRings> of Benzene • • The benzene molecule is a six-membered carbon ring with one hydrogen atom attached to each carbon. This arrangement leaves one electron from each carbon free to participate in a double bond. – Two different structures with alternating double bonds can be written for benzene. 54 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Benzene • is also represented as a hexagon with a circle drawn inside 55 Basic Chemistry Copyright © 2011 Pearson Education, Inc. The of Benzene 22.4Structure Hydrocarbon Rings> Drawing a solid or dashed circle inside a hexagon represents how the electrons are distributed. • However, the traditional structure, shown to the right in the series above, is used in this textbook. • Remember, though, that each bond in the ring is identical. 56 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Organic Chemistry Hydrocarbons ONLY Carbon and Hydrogen Alkene Alkyne other Substituded Hydrocarbons Alkane Ring :Aromatic (Benzene) Lab: building organic compounds