Download PowerPoint - Name Hydrocarbons - IUPAC Rules

Naming Hydrocarbons
(nomenclature)
Handout: Hydrocarbons: IUPAC names
Drawing structures: it’s all good
H
C
2-butene
H
H
H
C
C
C
C
H
H
H
H
H3C
H
CH3
C
H
CH
H3C
CH3
CH
CH3
H3C CH CH CH3
H3C
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
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
14
Alkene: C22H
44
H 3C
CH3
8 (2x5 - 2 = 10 - 2)
Naming: common vs. IUPAC
• Common names used in the 1800’s are still
used for some compounds today:
O
O
H
C
H
OH
Formic acid
C
C
Acetylene
H
C
H3C
CH3
Acetone
• 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 pent6 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 heptane, nonane
2C, 4C alkyne ethyne, butyne
1C, 3C alkene does not exist, propene
Mnemonic for first four prefixes
First four prefixes
•
•
•
•
MethEthPropBut-
Monkeys
Eat
Peeled
Bananas
Other prefixes
Decade
?
Decimal
• Pent• Oct-
• Dec-
Decathalon • Hex-, Hept-, Non-
Numbering carbons
Q- draw pentene
A- Where’s the bond? H3C
5
1
We number C atoms
H
H
1-pentene
C
C
C
C
H
H
H
H
4
2
3
2
4
1
5
H
• 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
H
C 2H 4
H3 C
C
2-butene
C
CH3
Ethene
H
H3C
CH3 3-nonyne
Multiple multiple bonds
H 3C
CH3 2,3-heptadiene
H3C
C
C
C
C
C
C
2,4,6-nonatriyne
•
•
•
•
CH2
CH3
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
H
H 2-butyne
HC C CH2
H
C
C
C
C
H
H2C
CH
1,2,4-pentatriene
CH3CH2CH2CH=C=CH2 1,2-hexadiene
H
H
Cyclic structures
H
H
H
H
C
C
C
H
• Cyclic structures are circular
C C
• Have “cyclo” in name
H
H
H
H
• 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
H
H
H2C
CH2
HC
CH
H
H
C
C
C
H
C
C
H
CH2
H
H 2C
CH2
Naming side chains
CH3
CH3
H3C
• Names are made up
of: side chains, root
• 2,3-dimethylpentane
CH3
• Root is the longest possible HC chain
• Must contain multiple bonds if present
• Add -yl to get name of side chain H C
CH3
3
• Common side chains include:
CH
CH3- methyl
CH3CH2- ethyl
*
CH3CH2CH2- propyl (CH3)2CH• isopropyl
“iso” (branched) is not an IUPAC convention
• Br- (bromo), Cl- (chloro), F- (fluoro), I- (iodo)
Naming side chains
Example: use the rules on the bottom of
handout to name the following structure
CH2
CH3 CH2 C
CH2 CH3
CH2 C
CH3
CH3
Rule 1: choose the correct ending
ene
Naming side chains
CH2
CH3 CH2 C
CH2 CH3
CH2 C
CH3
CH3
Rule 2: longest carbon chain
ene
Naming side chains
CH2
CH3 CH2 C
CH2 CH3
CH2 C
CH3
CH3
Rule 3: attach prefix (according to # of C)
1-hexene
ene
Naming side chains
CH2
CH3 CH2 C
CH2 CH3
CH2 C
CH3
CH3
Rule 4: Assign numbers to each carbon
1-hexene
Naming side chains
CH2
CH2 CH3
1
CH3 CH2 C
2
5
CH2 C
3
4
6
CH3
CH3
Rule 4: Assign numbers to each carbon
1-hexene
Naming side chains
CH2
ethyl
CH2 CH3
1
CH3 CH2 C
2
5
CH2 C
3
4
CH3
6
CH3
methyl
methyl
Rule 5: Determine name for side chains
1-hexene
Naming side chains
CH2
ethyl
CH2 CH3
1
CH3 CH2 C
2
5
CH2 C
3
4
CH3
6
CH3
methyl
methyl
Rule 6: attach name of branches
2-ethyl-4-methyl-4-methyl-1-hexene
1-hexene
Naming side chains
CH2
ethyl
CH2 CH3
1
CH3 CH2 C
2
5
CH2 C
3
4
CH3
6
CH3
methyl
methyl
Rule 7: list alphabetically
2-ethyl-4-methyl-4-methyl-1-hexene
1-hexene
Naming side chains
CH2
ethyl
CH2 CH3
1
CH3 CH2 C
2
5
CH2 C
3
4
CH3
6
CH3
methyl
methyl
Rule 8,9: group similar branches
2-ethyl-4-methyl-4-methyl-1-hexene
1-hexene
Naming side chains
CH2
ethyl
CH2 CH3
1
CH3 CH2 C
2
5
CH2 C
3
4
CH3
6
CH3
methyl
methyl
Rule 8,9: group similar branches
2-ethyl-4,4-dimethyl-1-hexene
Naming side chains
• Try PE 1 on pg. 1019 (answer to a is wrong)
H3C
H3C
CH2
CH CH3
H2C
CH2
CH CH CH2 CH3
H3C
CH3
3-methylhexane
CH2 CH2 CH3
CH
CH3
4-ethyl-2,3-dimethylheptane
CH3
CH3
CH3
CH3 CH2 CH CH CH CH2 CH CH3
CH2 CH3
5-ethyl-2,4,6-trimethyloctane
Naming side chains
Name the structures below
CH3
CH
H3C
CH2
CH
CH3
H2C
H3C
H3C
3-ethyl-2-methylpentane
CH3
CH3
3-ethyl-1,5,5trimethylcyclohexene
CH3
More practice
Br
4-bromo-7-methyl-2-nonene
Br
2,5-dibromo-6-chloro-1,3-cycloheptadiene
Br
Cl
CH3
H 3C
C
CH3
CH2 C
F
CH CH CH CH3
5-fluoro-7,7-dimethyl-2,4-octadiene
Pg. 1049 # 24.5, 24.6, 24.7, 24.14, 24.15
Ignore 24.15 e)
Pg. 1049
24.5 - 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).
24.15
2,2-dimethyloctane
1,3-dimethylcyclopentane
1,1-diethylcyclohexane
6-ethyl-5-isopropyl-7-methyl-1-octene
Aromatic nomenclature
H3C
There are 2 naming methods
H3C
1) Numbering carbons
2) ortho, meta, para (stomp) 1,2-dimethylbenzene
orthodimethylbenzene
CH3
ST Ortho
Meta
H3C
H3C
Para
Benzene is very stable
(does not generally
undergo addition)
1,3-dimethylbenzene
metadimethylbenzene
H3C
CH3
1,4-dimethylbenzene
paradimethylbenzene
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.
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