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Handout: Hydrocarbons: IUPAC names

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1 Handout: Hydrocarbons: IUPAC names
Naming Hydrocarbons (nomenclature) Handout: Hydrocarbons: IUPAC names

2 Drawing structures: it’s all good
2-butene This is called the “condensed structure” On a test, choose a method that shows all Hs CH3CH=CHCH3 Using brackets can also shorten some formulas: CH3(CH2)4CH3 vs. CH3CH2CH2CH2CH2CH3

3 Background: formulas for HCs
Alkanes= CnH2n+2, enes= CnH2n, ynes= CnH2n-2 Remember enes, then think of what would happen if bond was single or triple instead. Provides some useful information (e.g. for compositional analysis, or to check work) Cannot always tell hydrocarbon type based on numbers (e.g. propyne vs. propadiene) Q - how many hydrogens in each of these: 6 carbon alkane Alkene: C22H 14 44 8 (2x5 - 2 = )

4 Naming: common vs. IUPAC
Common names used in the 1800’s are still used for some compounds today: Acetone Formic acid Acetylene The International Union of Pure and Applied Chemistry (IUPAC) was established in 1900s Frequent revisions to nomenclature Systematic method allows an infinite number of compounds to be named given a few rules

5 Basic names of hydrocarbons
Hydrocarbon names are based on: 1) class 2) # of C, 3) side chain type and 4) position 1) name will end in -ane, -ene, or -yne 2) the number of carbons is given by a “Prefix” 1 meth- 2 eth prop- 4 but pent hex hept- 8 oct non 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 does not exist, propene

6 Mnemonic for first four prefixes
Monkeys Eat Peeled Bananas First four prefixes Meth- Eth- Prop- But-

7 ? Other prefixes Decade Decimal Decathalon Pent- Oct- Dec-
Hex-, Hept-, Non-

8 Numbering carbons 1-pentene Q- draw pentene A- Where’s the bond?
We number C atoms Thus, naming compounds with multiple bonds is more complex than previously indicated Only if 2+ possibilities exist, are #s needed Always give double bond the lowest number Q - Name these C2H4 2-butene Ethene 3-nonyne

9 Multiple multiple bonds
2,3-heptadiene 2,4,6-nonatriyne Give 1st bond (1st point of difference) lowest # include di, tri, tetra, penta, etc. before ene/yne Comma between #s, hyphen between #-letter You do not need to know ene + yne CH3CH2CH2CH=C=CH2 2-butyne 1,2,4-pentatriene 1,2-hexadiene

10 Cyclic structures Cyclic structures are circular Have “cyclo” in name
Benzene is not a cyclic structure cyclopentane Q- Draw these (note: carbons in a double bond should be consecutive- 1 and 2, 5 and 6, etc.): cyclobutene 1,3-cyclopentadiene cyclopropane

11 Naming side chains Names are made up of: side chains, root
3 Names are made up of: side chains, root 2,3-dimethylpentane Root is the longest possible HC chain Must contain multiple bonds if present Add -yl to get name of side chain Common side chains include: CH3- methyl CH3CH2- ethyl CH3CH2CH2- propyl (CH3)2CH- isopropyl “iso” (branched) is not an IUPAC convention Br- (bromo), Cl- (chloro), F- (fluoro), I- (iodo)

12 Naming side chains Example: use the rules on the bottom of handout to name the following structure Rule 1: choose the correct ending ene

13 Naming side chains Rule 2: longest carbon chain ene

14 Naming side chains Rule 3: attach prefix (according to # of C) ene

15 Naming side chains Rule 4: Assign numbers to each carbon 1-hexene

16 Naming side chains Rule 4: Assign numbers to each carbon 1-hexene

17 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

18 Naming side chains Rule 6: attach name of branches
ethyl methyl methyl Rule 6: attach name of branches 2-ethyl-4-methyl-4-methyl-1-hexene 1-hexene

19 Naming side chains Rule 7: list alphabetically
ethyl methyl methyl Rule 7: list alphabetically 2-ethyl-4-methyl-4-methyl-1-hexene 1-hexene

20 Naming side chains Rule 8,9: group similar branches
ethyl methyl methyl Rule 8,9: group similar branches 2-ethyl-4-methyl-4-methyl-1-hexene 1-hexene

21 Naming side chains Rule 8,9: group similar branches
ethyl methyl methyl Rule 8,9: group similar branches 2-ethyl-4,4-dimethyl-1-hexene

22 Naming side chains Try PE 1 on pg. 1019 (answer to a is wrong)
3-methylhexane 4-ethyl-2,3-dimethylheptane 5-ethyl-2,4,6-trimethyloctane

23 Naming side chains Name the structures below 3-ethyl-2-methylpentane

24 More practice 4-bromo-7-methyl-2-nonene 2,5-dibromo-6-chloro-1,3-cycloheptadiene 5-fluoro-7,7-dimethyl-2,4-octadiene Pg # 24.5, 24.6, 24.7, 24.14, 24.15 Ignore e)

25 Pg. 1049 Recall, the exceptions to organic compounds are oxides of carbon, carbonates, bicarbonates, cyanides. b) is an oxide, d) bicarbonate, e) carbonate This is a straight chain molecule as all carbons are consecutive. none are possible: a) one too few Hs (should be CH3CH2CH3), b) one H too many (should be CH2=CHCH2CH3), c) one H too many (should be CH3CH=CHCH2CH3).

26 24.15 2,2-dimethyloctane 1,3-dimethylcyclopentane
1,1-diethylcyclohexane 6-ethyl-5-isopropyl-7-methyl-1-octene

27 Aromatic nomenclature
There are 2 naming methods Numbering carbons ortho, meta, para (stomp) 1,2-dimethylbenzene orthodimethylbenzene ST Ortho Meta 1,3-dimethylbenzene metadimethylbenzene Para Benzene is very stable (does not generally undergo addition) 1,4-dimethylbenzene paradimethylbenzene

28 For more lessons, visit
More practice Build a molecule that can be named according to the rules that we have talked about. Make it challenging. Place your model at a vacant lab station. On a scrap piece of paper write the following: 1) your station number, 2) the structure of your molecule, 3) the name of the structure. Give this to your teacher. Rotate through the stations, drawing the structures and determining their names. At the end of the class students will reveal the answer with an explanation. For more lessons, visit

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