Naming Hydrocarbons (nomenclature)

Drawing Structures: It’s All Good 2-butene This is called the “condensed structure” CH3CH=CHCH3 Using brackets can also shorten some formulas: CH3CH2CH2CH2CH2CH3 vs. CH3(CH2)4CH3

Basic Naming of Hydrocarbons Hydrocarbon names are based on: 1) type, 2) # of carbons, 3) side chain type and position 1) name will end in -ane, -ene, or -yne 2) the number of carbons is given by a “prefix” 1 meth- 2 eth- 3 prop- 4 but- 5 pent- 6 hex- 7 hept- 8 oct- 9 non- 10 dec- Actually, all end in a, but a is dropped when next to a vowel. E.g. a 6 C alkene is hexene Q - What names would be given to these: 7C, 9C alkane 2C, 4C alkyne 1C, 3C alkene heptane, nonane ethyne, butyne methene, propene

Mnemonic for First Four Prefixes Monkeys Eat Peeled Bananas First four prefixes Meth- Eth- Prop- But-

? Other Prefixes Decade Decimal Decathalon Pent- Oct- Dec- Hex-, Hept-, Non- Mother Eats Peanut Butter Pickles Having Ham On Numbered Dishes

What are the 3 classes of hydrocarbons, based on number of carbon-carbon bonds? Give the 10 organic homologous prefixes, in order, from 1-10. Name these compounds: C2H4

Numbering Carbons 1-pentene Q- draw 1-pentene A- Where’s the double bond? We # C atoms. Naming compounds with multiple bonds is more complex than previously indicated. When 2+ possibilities exist, #s are needed. Always give double bond the lowest number. Q - Name these H H H H H3 C C C C H3 H C C C H C C C H H H H H H

Name the 4 groups of hydrocarbons. (alphabetically) Draw the structures for the following compounds: 2-octene 4-decyne hexane 3, 4, 5 – triethyldecane 2-chloro – 4 – methyl – nonane

Naming Side Chains C H 3 The names of molecules with branches are based on: side chains, root 2,3-dimethylpentane The “root” or “parent chain” is usually the longest possible hydrocarbon chain. The root must include multiple bonds if they are present. If a cyclic structure is present it will be the root even if it is not the longest chain. Side chains are also called “side branches” or “alkyl groups”. Their names end in -yl. Common side chains : -CH3 methyl, -CH2CH3 ethyl, -CH2CH2CH3 propyl

IUPAC Rules for Naming Hydrocarbons Choose the correct ending: -ane, -ene, or -yne Determine the longest carbon chain. Where a double or triple bond is present, choose the longest chain that includes this bond. If there is a cyclic structure present, the longest chain starts and stops within the cyclic structure. Assign numbers to each C of the parent chain. For alkenes and alkynes the first carbon of the multiple bond should have the smallest number. For alkanes the first branch (or first point of difference) should have the lowest #. Carbons in a multiple bond must be numbered consecutively. Attach a prefix that corresponds to the number of carbons in the parent chain. Add cyclo- to the prefix if it is a cyclic structure.

IUPAC Rules for Naming Hydrocarbons Determine the correct name for each branch (“alkyl” groups include methyl, ethyl, propyl, etc.) Attach the name of the branches alphabetically, along with their carbon position, to the front of the parent chain name. Separate numbers from letters with hyphens (e.g. 4-ethyl-2-methyldecane) When two or more branches are identical, use prefixes (di-, tri-, etc.) (e.g. 2,4-dimethylhexane). Numbers are separated with commas. Prefixes are ignored when determining alphabetical order. (e.g. 2,3,5-trimethyl-4-propylheptane) When identical groups are on the same carbon, repeat the number of this carbon in the name. (e.g. 2,2-dimethylhexane)

Example: use the rules on this handout to name the following structure Naming Side Chains Example: use the rules on this handout to name the following structure Rule 1: choose the correct ending ene

Naming Side Chains Rule 2: determine the longest carbon chain ene

Naming Side Chains Rule 3: Assign numbers to each carbon ene

Naming Side Chains Rule 3: Assign numbers to each carbon ene

Naming Side Chains Rule 4: attach prefix (according to # of Cs) ene 1-hexene

Naming Side Chains Rule 5: Determine name for side chains 1-hexene ethyl methyl methyl Rule 5: Determine name for side chains 1-hexene 1-hexene

Naming Side Chains 2-ethyl-4-methyl-4-methyl-1-hexene 1-hexene Rule 6: attach name of branches alphabetically 2-ethyl-4-methyl-4-methyl-1-hexene 1-hexene

Naming Side Chains Rule 7,8: group similar branches ethyl methyl methyl Rule 7,8: group similar branches 2-ethyl-4-methyl-4-methyl-1-hexene 1-hexene

Naming Side Chains Rule 7,8: group similar branches ethyl methyl methyl Rule 7,8: group similar branches 2-ethyl-4,4-dimethyl-1-hexene

propene 2,4-dimethyl-2-pentene 2-butene 1-butyne

For more lessons, visit www.chalkbored.com a) 3,3-dimethyl-1-pentene b) same C H C H 3 3 C H C C C H C H C H 3 2 C H C H 2 3 c) 5-ethyl-4-methyl-2-heptyne For more lessons, visit www.chalkbored.com

3 – methyl-1,3-cyclopentene 2-ethyl-2-pentene Name: 3. 4. Draw 3 – methyl-1,3-cyclopentene 2-ethyl-2-pentene Name: 3. 4. 5. Give both names!

Isomers Same molecular formula, different molecular structures. Two types: structural and geometric isomers. 1. Structural Isomers: molecules with same chemical formula, but different molecular structures. butane (C4H10) 2 – methylpropane (C4H10) CH3 CH3-CH2-CH2-CH3 CH3-CH-CH3

Isomers (cont’d) 2. Geometric Isomers: differ only in the geometry of their substituted groups. cis- 2 - butene trans- 2 - butene cis-configuration: substituted groups are on the same side as the double bond. trans-configuration: substituted groups are on the opposite sides of the double bond.

1. Draw the structural formulas: 3. Name the following: a) 3-ethyl-1,4-cyclopentene b) 1-chloro-2,3,4-triethyl-3-heptene C = C c) 2-fluoro-7,7-dimethyl-4-decyne 2. Draw the cis and trans forms of the C = C following alkenes: a) 2-pentene 4. Identify the asymmetric b) 2-octene carbon, if any: c) 2-methyl-2-heptene a) CH3CH2CHO d) 2,3-dimethyl-2-butene b) CH3CHOH H H a) CH3 CH2CH2CH3 CH3 CH3 b) CH3 CH3 CH3

Isomers (cont’d) Stereoisomers: molecules of the same molecular structure that differ only in the arrangement of the atoms in space. They are mirror images of each other (think right and left hands.)

Isomers (cont’d) Stereoisomers: molecules of the same molecular structure that differ only in the arrangement of the atoms in space. They are mirror images of each other (think right and left hands.) Left-handed (S)

Isomers (cont’d) Stereoisomers: molecules of the same molecular structure that differ only in the arrangement of the atoms in space. They are mirror images of each other (think right and left hands.) Left-handed (S) Right-handed (R)

Isomers (cont’d) Stereoisomers: molecules of the same molecular structure that differ only in the arrangement of the atoms in space. They are mirror images of each other (think right and left hands.) “left-handed” “right-handed”

Aromatic Hydrocarbons Aromatic hydrocarbons are hydrocarbons that have six-membered carbon rings and delocalized electrons. Benzene is the primary aromatic hydrocarbon. Benzene has the chemical formula C6H6 and can also be thought of as 1,3,5-cyclohexatriene (hexene). Benzene can also be represented graphically like this.

Isomers (cont’d) Cl C Br H F Asymmetric Carbon: a carbon with four different groups attached to it. Cl C Br H F Chlorofluorobromomethane

Functional Groups Besides our basic hydrocarbon classes, we can add other elements/ions, groups of elements to an organic structure = Functional Groups R = radical or, in this case, represents C Alcohols (R-OH), ethers (R-O-R), carboxylic acids (R-COOH), aldehydes (R-COH) – what are the others presented in the book? Identifying these! Naming these (all have their own endings)!

Classes of Organic Compounds A functional group gives an organic compound properties that are very different from those of corresponding hydrocarbons. Some examples: 1. Alcohols: are organic compounds that contain one or more hydroxyl groups. The general formula for alcohols is R-OH (rememeber that “R” stands for the rest of the molecule.) Glycerol: 1,2,3-propanetriol Ethanol: 1-ethanol

Classes of Organic Compounds (cont’d) 2. Ethers: are organic compounds in which two hydrocarbon groups are bonded to the same oxygen atom. This can can be represented by the formula R-O-R. Diethyl Ether: Dioxane: Dimethyl Ether:

Classes of Organic Compounds (cont’d) 3. Aldehydes and ketones: contain the carbonyl group: Aldehyde: organic compound in which the carbonyl group is attached to a carbon atom at the end of a carbon chain. Ketone: organic compound in which the carbonyl group is attached to carbon atoms within the chain. Aldehyde Ketone

Classes of Organic Compounds (cont’d) 4. Carboxylic Acids: are organic compounds that contain the carboxyl functional group. A member of this class of organic compounds can be represented by the general formula: 5. Esters: are organic compounds that have carboxylic acid groups in which the hydrogen of the hydroxyl group has been replaced by an alkyl group. Observe:

Classes of Organic Compounds (cont’d) Many esters have distinctive fruit-like odors, which has led to their commonplace use in artificial flavorings and fragrances. Examples: