Number of carbon atoms. 3 propane 8 octane. 4 butane 9 nonane. 5 pentane 10 decane

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1 Name: Date: Pd: Accelerated Chemistry - Naming Hydrocarbons Alkane Nomenclature 1. Alkanes are saturated hydrocarbons, with each C bonded to as many atoms as possible (4 other atoms, C or H). For example, in ethane, C 2 H 6, both carbons are making four bonds. Each carbon is bonded to the other carbon and three hydrogen atoms. 2. The names of the first ten alkanes are given below. As you can see, each name is composed of a prefix, followed by -ane (designating an alkane). The prefix indicates the number of carbons atoms in the backbone carbon chain. The prefix designates the length of the chain. Fill in the formulas of the alkanes. Number of carbon atoms Name Molecular formula Number of carbon atoms Name 1 methane CH 4 6 hexane Molecular formula 2 ethane C 2 H 6 7 heptane 3 propane 8 octane 4 butane 9 nonane 5 pentane 10 decane 3. The parent name of the hydrocarbon is that given to the longest continuous chain of carbon atoms in the molecule. The compound below is 3-methylpentane CH CH 2 CH 2 4. An alkane minus one hydrogen atom is an alkyl group. For example, when a hydrogen atom is removed from methane, we are left with the fragment, which is called a methyl group. Similarly, removing a hydrogen atom from the ethane molecule gives an ethyl group, or C 2 H 5. Any chain branching off the longest chain is named as an alkyl group. 5. When one or more hydrogen atoms are replaced by other groups, the name of the compound must indicate the locations of carbon atoms where replacements are made. The procedure is to number each carbon atom on the longest chain in the direction that gives the smaller number for the locations of all branches. This is 3-ethylhexane, not 4-ethylhexane. CH 2 CH 2 CH CH 2 6. CH 2 7. When there is more than one alkyl branch of the same kind present, we use a prefix such as di-, tri-, or tetra- with the name of the alkyl group. When there are two or more different alkyl branches, the name of each branch, with its position number, precedes the base name. C CH 2 2,2-dimethylbutane CH CH 2,3-dimethylbutane 1

2 8. When there are two or more different alkyl branches, the name of each branch, with its position number, precedes the base name. For example, 4-ethyl-3,3-dimethylheptane; the substituents are named alphabetically (the mono-, di-, etc. designations are not included in determining alphabetical order): C 2 H 5 CH 2 C CH CH 2 CH 2 Alkene and Alkyne Nomenclature Alkenes and alkynes are unsaturated hydrocarbons, with at least 2 C s bonded to less than 4 other atoms, and hence containing double or triple bonds. H H C C H H CH 2 CH 2 C 2 H 4 Structural formula Condensed formula Molecular formula The parent hydrocarbon is determined by the number of carbon atoms in the longest continuous chain containing the double bond. Numbering is done in the direction that gives the lowest number to the double bond, or the lowest number at the first point of difference. If there are different substituents at equivalent positions on the chain, the substituent of lower alphabetic order is given the lowest number. CH CH 2 CH 2 =CH-CH 2 1-butene CH 2 CH 3-methyl-1-pentene 3-methyl-1-pentene (The 1 in front of the name of the parent chain tells you where the double bond is located.) You may also write it as 3-methyl-pent-1-ene. Molecules having at least one double bond may produce geometric isomers. Since rotation about a double bond is restricted, the parts of the molecule on either side of a double bond remain in fixed positions. The compound 1,2-dichloroethene demonstrates this property in its cis- and trans- forms. Positional isomers differ in the location of atoms attached to the carbon backbone. 1,1- dichloroethene is a positional isomer of 1,2-dichloroethene. How many isomers does 1,1- dichloroethene have? Specify the geometric isomer (if necessary). Cl Cl C C H H cis-1,2-dichloroethene Cl H C C H Cl trans-1,2-dichloroethene I. Practice Finding the stem. Find the longest continuous chain of carbon atoms. Circle the chain. Name it. The first one is done for you. Circle the parent chain, and then name the hydrocarbons. Octane 2

3 II. Naming Alkanes Name the following alkanes by first circling the longest chain and naming it. Then, follow the rules for naming the substituents. Make sure each substituent has a number and they are placed in alpha order! The first one is done for you methyl-hexane CH CH 2 CH 2 CH 2 CH 2 CH 2 8. CH 2 CH 2 CH 2 CH CH 2 CH 2 CH 2 CH 2 CH 2 CH CH 2 CH CH 2 9. df 3

4 III. Drawing Structures of Alkanes: Draw the structures for the following alkanes or answer the questions. (Begin by drawing the longest continuous chain, then add the braches. To add in the hydrogens, remember each carbon makes 4 bonds.) 10. 2,2-dimethylpentane 11. chloroethane 12. 1,2-dibromopropane ethyl-2-methylcyclopentane 14. Draw structural formulas for possible isomers with the formula C 3 H 6 Cl 2. Name each isomer. 15. What s wrong with these names? Draw them as they are named below to try to figure out what is wrong: a. 2-ethylbutane b. 3,4-dimethylpentane 16. The molecule 3- ethylhexane is a structural isomer of which straight-chain alkane? 4

5 17. The molecule 4- propylheptane is a structural isomer of which straight-chain alkane? IV. Naming Alkenes, Alkynes and Rings. Example: Make sure the longest chain contains the double bond and you indicate where it is located. Name Formula CH 2 CH 2 C CH 2 CH 2 CH 2 5

6 V. Drawing Structures of Alkenes, Alkynes and Rings. 2,3 dimethyl 1-hexene 3. 2,3 dimethyl 1-cyclohexene 1. 2-methyl 1,3-propadiene 4. 4,6 diethyl 2-octyne ,6-dimethyl-3-heptene 6. 5-ethyl-2-heptyne 7. Draw structural formulas and name the four alkenes that have the formula C 4 H 8. (Consider cis and trans) 8. Draw structures for the cis and trans isomers of 4-methyl-2-hexene. Name each isomer. 6

7 P2 P4 E2 VI. Naming Alcohols Examples: P5 P3 E3 1-propanol or propan-1-ol 2-propanol or propan-2-ol 2-methyl-2-propyl-pentan-1-ol Practice Problems: Multiple OH Groups: Multiple OH Example & Practice: Two -OH is a & Three -OH is a Draw & Name 3 isomers of C 5 H 11 OH. 7

8 VII. Vocabulary Review! Complete the sentence or answer the question. 9. In saturated organic compounds, all the bonds between carbon atoms are. 10. The existence of two or more substances with the same molecular formula but different structural formulas is known as. 11. Compounds with the same atoms bonded in the same order but with different arrangement of atoms around a double bond are examples of. 12. cyclohexane 22. cyclopropane 24. cycloctane 13. cyclopentane 23. cycloheptane 25. cyclobutane 8