Handout: Hydrocarbons: IUPAC names
Naming Hydrocarbons (nomenclature)
Drawing structures: it’s all good
CH3
CH
CH
CH3
CH3
CH3
CH3
CHCH
CH3
2-butene
This is called the “condensed structure”
C C C C
H
H
H
H H H
H
H
CH3 CH CH CH3
On a test, choose a method that shows all HsCH3CH=CHCH3
Using brackets can also shorten some formulas: CH3(CH2)4CH3 vs. CH3CH2CH2CH2CH2CH3
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 alkaneAlkene: C22H
14448 (2x5 - 2 = 10 - 2)CH3 CH3
Naming: common vs. IUPAC• Common names used in the 1800’s are still
used for some compounds today:
H C C HAcetylene
O
CCH3CH3
AcetoneFormic acid
C
O
OHH
• 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
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- 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 alkane2C, 4C alkyne1C, 3C alkene
heptane, nonaneethyne, butynedoes not exist, propene
Mnemonic for first four prefixes
First four prefixes• Meth-
• Eth-
• Prop-
• But-
Monkeys
Eat
Peeled
Bananas
?Decade
Decimal
Decathalon
Other prefixes
• Pent-
• Oct-
• Dec-
• Hex-, Hept-, Non-
Numbering carbonsQ- draw penteneA- 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
C C C CCH3
H
H
H
H H H
HCH31
C2
C3
C4
C5
H
H
H
H H H
HCH35
C4
C3
C2
C1
H
H
H
H H H
H
Ethene
3-nonyne
2-buteneCH3
CH
CH
CH3
CH3 CH3
C2H4
1-pentene
Multiple multiple bonds
• 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
2,3-heptadieneCH3CH3
CH3
CH2CCCCCCCH32,4,6-nonatriyne
C C C C
H
H
H
H
H
H
CH3CH2CH2CH=C=CH2
CH2CCH
CHCH2
2-butyne
1,2-hexadiene1,2,4-pentatriene
C
C
C
CC H
HHH
H
H
HH H
H
Cyclic structures• Cyclic structures are circular• Have “cyclo” in name• Benzene is not a cyclic structure
• cyclopentaneQ- Draw these (note: carbons in a double bond
should be consecutive- 1 and 2, 5 and 6, etc.): cyclobutene 1,3-cyclopentadiene cyclopropane
CH2
CH
CH2
CHCC
C CCH
H H
H
H H
CH2
CH2
CH2
CH3 CH3
CH3
CH3Naming side chains
• Names are made up of: side chains, root
• 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
• 2,3-dimethylpentane
CH3 CH3
CH3
CH3
CH3CH
CH3
*
• “iso” (branched) is not an IUPAC convention• Br- (bromo), Cl- (chloro), F- (fluoro), I- (iodo)
ene
Naming side chainsExample: use the rules on the bottom of
handout to name the following structure
CH3 CH2 C
CH2
CH2 C
CH2
CH3
CH3
CH3
Rule 1: choose the correct ending
ene
Rule 2: longest carbon chain
Naming side chains
CH3 CH2 C
CH2
CH2 C
CH2
CH3
CH3
CH3
1-hexene ene
Rule 3: attach prefix (according to # of C)
Naming side chains
CH3 CH2 C
CH2
CH2 C
CH2
CH3
CH3
CH3
Rule 4: Assign numbers to each carbon
1-hexene
Naming side chains
CH3 CH2 C
CH2
CH2 C
CH2
CH3
CH3
CH3
Rule 4: Assign numbers to each carbon
CH3 CH2 C2
CH21
CH23
C4
CH25
CH3
CH3
CH36
CH3 CH2 C
CH2
CH2 C
CH2
CH3
CH3
CH3
1-hexene 1-hexene
Naming side chains
CH3 CH2 C2
CH21
CH23
C4
CH25
CH3
CH3
CH36
Rule 5: Determine name for side chains
CH3 CH2 C
CH2
CH2 C
CH2
CH3
CH3
CH3
1-hexene 1-hexene
Naming side chains
ethyl
methyl
methyl
CH3 CH2 C
CH2
CH2 C
CH2
CH3
CH3
CH3
CH3 CH2 C2
CH21
CH23
C4
CH25
CH3
CH3
CH36
1-hexene2-ethyl-4-methyl-4-methyl-1-hexene
Naming side chains
ethyl
methyl
methyl
Rule 6: attach name of branches
Rule 7: list alphabetically
CH3 CH2 C
CH2
CH2 C
CH2
CH3
CH3
CH3
CH3 CH2 C2
CH21
CH23
C4
CH25
CH3
CH3
CH36
1-hexene2-ethyl-4-methyl-4-methyl-1-hexene
Naming side chains
ethyl
methyl
methyl
Rule 8,9: group similar branches
CH3 CH2 C
CH2
CH2 C
CH2
CH3
CH3
CH3
CH3 CH2 C2
CH21
CH23
C4
CH25
CH3
CH3
CH36
1-hexene2-ethyl-4-methyl-4-methyl-1-hexene
Naming side chains
ethyl
methyl
methyl
Rule 8,9: group similar branches
CH3 CH2 C
CH2
CH2 C
CH2
CH3
CH3
CH3
CH3 CH2 C2
CH21
CH23
C4
CH25
CH3
CH3
CH36
2-ethyl-4,4-dimethyl-1-hexene
Naming side chains
ethyl
methyl
methyl
Naming side chains• Try PE 1 on pg. 1019 (answer to a is wrong)
CH3 CH2
CH CH3
CH2CH2
CH3
CH3 CH
CH
CH3
CH
CH3
CH2 CH2 CH3
CH2 CH3
CH3CH2CH CH CH CH2CH CH3
CH3
CH2CH3
CH3 CH3
3-methylhexane4-ethyl-2,3-dimethylheptane
5-ethyl-2,4,6-trimethyloctane
Naming side chains
3-ethyl-2-methylpentane
3-ethyl-1,5,5-trimethylcyclohexene
CH3CH
CHCH2
CH3
CH3
CH2CH3
CH3 CH3
CH3CH3
Name the structures below
More practice
4-bromo-7-methyl-2-nonene
5-fluoro-7,7-dimethyl-2,4-octadiene
BrBr Br
Cl
CH3 C CH2C CH CH CH CH3
CH3
CH3
F
2,5-dibromo-6-chloro-1,3-cycloheptadiene
Pg. 1049 # 24.5, 24.6, 24.7, 24.14, 24.15Ignore 24.15 e)
Pg. 104924.5 - Recall, the exceptions to organic
compounds are oxides of carbon, carbonates, bicarbonates, cyanides.b) is an oxide, d) bicarbonate, e) carbonate
24.6 - This is a straight chain molecule as all carbons are consecutive.
24.7 - 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).
24.152,2-dimethyloctane
1,3-dimethylcyclopentane
1,1-diethylcyclohexane
6-ethyl-5-isopropyl-7-methyl-1-octene
There are 2 naming methods1) Numbering carbons2) ortho, meta, para (stomp)
Aromatic nomenclature
CH3
Ortho
Para
ST Meta
CH3
CH3
CH3
CH3
CH3CH3
1,2-dimethylbenzeneorthodimethylbenzene
1,3-dimethylbenzenemetadimethylbenzene
1,4-dimethylbenzeneparadimethylbenzene
Benzene is very stable (does not generally undergo addition)
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 www.chalkbored.com
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