Idea Transcript
Nomenclature Worksheet 1 NAMING ALKANES AND CYCLOALKANES Model 1: Alkane Nomenclature alkane = molecule consisting entirely of carbon and hydrogen atoms connected by single bonds
Critical Thinking Question 1.
Cross out each molecule below that is NOT an alkane. H
H
CH3
C
H
H3C
H2 C
CH3
CH3
H3C
H CH3
H3C
CH3Cl
CH3
H3C
CH3
H3C
O
C H
C CH3
H3C
Memorization Task NW1.1: Memorize the names of the straight-chain alkanes below #C’s
Condensed Structure
Name
1
CH4
2
CH3CH3
3
CH3CH2CH3
4
CH3CH2CH2CH3
butane
5
CH3CH2CH2CH2CH3
pentane
6
CH3CH2CH2CH2CH2CH3
hexane
7
CH3CH2CH2CH2CH2CH2CH3
heptane
8
CH3CH2CH2CH2CH2CH2CH2CH3
octane
9
CH3CH2CH2CH2CH2CH2CH2CH2CH3
nonane
10
CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3
decane
methane ethane propane
Critical Thinking Questions 2.
(E) Write a correct name below each of the unbranched alkanes in CTQ 1.
3.
(E) What suffix do all the names in Model 1 have in common with each other?
4.
(E) What prefix stands for eight carbons?
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CH3
C H2
H2 C
C
CH
H3C
H3C
CH3
OH Br
C
C H2
H2 C
H2 C
CH3
CH
CH3
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Nomenclature Worksheet 1
5.
parent chain = longest continuous chain found in a branched molecule. Circle and name the parent chain in each molecule below. The first one is done as an example.
H3C
CH3
H3C
CH
CH3
H2 C
CH3
C H2
H2 C
CH
H2 C
H3C
CH
CH
H3C
CH
H2C
C H2
H2 C C H2
CH3 C H2
CH CH3
H3C
CH2
CH3
CH3
Parent chain = heptane
6.
H2 C
A molecule can have more than one parent chain of equal length. Mark the alternate seven-carbon parent chain in the heptane example molecule above. (In this case, the two parent chains are equivalent, but as we will see later on, it sometimes matters which parent chain you choose.)
Model 2: Naming Branched Alkanes (Alkyl Groups) The parent chain name serves as the main part of the name of a branched alkane. For example: CH3 H3C 1
2 CH CH3
CH 3
4 CH
H2 C 5
H2 C
H3C 6 C H2
CH3 7
CH3
2,3,4-trimethylheptane
CH CH3
H2 C CH
CH3
H2 C
H3C C H2
H2C
C H2
H2 C C
H3C
CH3
4-ethyl-2-methylhexane
H2 C
CH3 CH3
3,3-dimethyloctane
Critical Thinking Questions 7.
Number the carbons in each parent chain in the structures in Model 2. By convention, numbering of a parent chain starts from the end nearest a branch. (The first one is done for you.)
8.
Underline the parent name in each chemical name in Model 2, and confirm that the parent chain matches this name. (The first one is done for you.)
9.
According to the examples in Model 2, what word in a name signifies a… a.
one-carbon branch?
b.
two-carbon branch?
10. Use Model 1 to propose names for three-, four-, five-, and six-carbon branches that follow the same pattern as “methyl” and “ethyl” for one- and two-carbon branches, respectively. (Note: The names of seven-, eight-, etc. carbon branches follow the same pattern, but branches of such length are rare since they are usually the parent chain.)
11. What information do the numbers in the names in Model 2 convey?
12. What do the words “di” and “tri” in the names in Model 2 convey?
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Nomenclature Worksheet 1
13.
75
(Check your work.) Do your answers to CTQ 10 fit the data in Memorization Task NW1.2 below?
Memorization Task NW1.2: Names of commonly found branches (“alkyl groups”) # C’s
Structure
IUPAC Name
Alternate IUPAC Name
1 2 3
–CH3 –CH2 CH3 –CH2 CH2 CH3
methyl ethyl propyl
n-propyl or propan-1-yl
CH
isopropyl
propan-2-yl
–CH2 CH2 CH2 CH3
butyl
n-butyl or butan-1-yl
isobutyl
2-methylpropan-1-yl
sec-butyl
butan-2-yl
tert-butyl
t-butyl (looks like a T!) or 2-methylpropan-2-yl
H3C
3 H3C
4
CH3
4
CH H3C
C H2
H 3C CH
4
H2C CH3 CH3
4
H 3C
C CH3
5 –CH2CH2 CH2 CH2 CH3 pentyl pentan-1-yl Multiple different branches are listed in a name alphabetically (not including prefixes di, tri, sec, or tert).
Critical Thinking Questions 14. Name the following alkanes. H2 C H3C
H2 C
H3C C H2
CH3 C
CH H3C
CH
H2 C
H3C
H2 C
CH2 CH
H2 C
H3C CH3
CH H2 C
H3C CH
CH2 CH
CH3 CH3
H2C
CH3 CH3
CH3
H2 C
H2C C H2
CH3 C H2
15. (Check your work.) Explain what is wrong with each of the following names for the first molecule above: a.
4,4-dimethylpentane
b.
1,1,1-trimethylbutane
c.
2,2-methylpentane
d.
2-dimethylpentane
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76
Nomenclature Worksheet 1
16. (Check your work.) Explain what is wrong with each of the following names for the third molecule in CTQ at the bottom of the previous page. a.
6-ethyl-2-methyl-4-pentyloctane
b.
3-methyl-5-isobutyldecane (Hint: Read the rule at the bottom of Memorization Task NW1.2)
17. Draw the following alkanes a.
2,3,3-trimethylpentane
b.
3-ethyl-2,5-dimethylhexane
Model 3: Cyclic Alkanes •
If a ring is present in a molecule, this ring almost always is considered the parent chain.
•
Number alkyl groups starting with one, and number around the ring toward the closest group.
•
If there are exactly two alkyl groups, decide which gets “1” based on alphabetical order.
Examples CH2CH3 CH3
CH H2C
CH
CH
CH H3C
CH3
H2C
CH2
H2C
C H2
CH
H3C
CH3
CH2CH3 CH
CH
H2C
CH CH2
CH3
2-ethyl-1,4-dimethylcyclohexane
1,2,3-trimethylcyclopentane
1-ethyl-2-methylcyclobutane
Critical Thinking Questions 18. What prefix is used to indicate that a parent chain (e.g., hexane) is cyclic? 19. Draw structures that correspond to the following names: a.
3-methylhexane
b.
1,1-diethylcyclobutane
c.
1-t-butyl-4-methylcyclohexane
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77
Nomenclature Worksheet 1
20.
For mono-substituted cycloalkanes the “1” is not included. That is, the name 1-methylcyclohexane is not correct. The correct name is simply “methylcyclohexane”. a.
Draw methylcyclohexane.
b.
Explain why adding a “1” to methylcyclohexane does not add any new information.
21. Write a correct name for each of the following structures: H3C
CH3 H3C
CH3
CH CH
CH3 H2C
CH
C
CH3
CH2
C H2
H2 C
C H2
CH CH2 CH
CH CH
CH3
C H2
H2 C
CH2 H3C
CH H2C
H2 C
H3C
CH2
CH
H3C CH
H2 C
CH
C H2
H3C
H3C
CH2
CH2
CH
H3C
CH3
Model 4: Alternate IUPAC Strategy for Naming Alkyl Sidechains side chain = a group that is not part of the parent chain. Side chains are boxed in the diagram below. CH3 H3C methyl
CH3
C H2
CH C H2
CH
H3C
H2 C
H2 C C H2
H2 C
CH3 C H2
CH C H2
H2 C
H3C
isopropyl
CH H2 C
CH H3C
CH3
H3C
C H2
CH2
CH
CH3
H2 C
CH
H2 C
C H2
CH
H3C CH3
sec-butyl
7-sec-butyl-6-isopropyl-2-methyldodecane
(2-methylhexan-3-yl)
CH
C H2
CH C H2
H2 C
CH3 C H2
CH3 C H2
(pentan-3-yl)
6-(2-methylhexan-3-yl)-7-(pentan-3-yl)dodecane
Critical Thinking Questions 22. What two-letter suffix appears to be common to the names of all side chains? 23. On the right-hand structure, what information is conveyed by the number preceding each “yl”?
24. Next to the isopropyl and sec-butyl side chains above, write their names based on the alternate naming strategy used to generate the names (2-methylhexan-3-yl) and (pentan-3-yl). 25. Is your answer to the previous question consistent with the last column in Mem. Task NW1.2? 26. Write the name of the molecule on the left using alternate side chain names (where applicable).
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78
Nomenclature Worksheet 1
Exercises 1.
Construct an explanation for why the following molecule is called methylpropene instead of 2-methyl-1-propene. CH3
H2C
C CH3
methylpropene
2.
3.
Draw the following molecules: a.
2,2,3,3-tetramethyl-6-propyldodecane
b.
2-methyl-3-ethyl-4-isobutyldecane
c.
tert-butylcyclopentane
d.
4-t-butyl-2,6-dimethylheptane
e.
4-isopropylheptane
f.
2,3-dimethyl-4-propyloctane
g.
6-(3-methylbutan-1-yl)-7-(2-methylpentan-2-yl)-4-(propan-2-yl)dodecane
h.
4,4-dimethyl-5-(2,4-dimethylpentan-3-yl)decane
i.
1,3,5-trimethylcyclohexane
j.
(3-propylheptan-2-yl)cyclohexane
Name each of the following structures.
H3C
H2C CH
CH2
CH
CH3
H3C H3C
CH3
C
CH
C H2
H3C H3C
CH3
CH3
H3C
H2 C
H2 C
H2 C
CH3
H3C
H2 C CH
CH
H2 C H3C
CH2 CH
CH C H2
CH H3C
CH3
H2 C
C H2
CH C H2
H2 C
CH2 H3C CH
CH2 H3C
CH3
H2 C
CH2 H3C
CH
H3C
H2 C
CH C H2
CH
C H2
CH3
CH3 C H2
CH CH
CH3 CH
H2C CH3
CH
H3C
CH3
CH3
CH3
H2 C
H3C CH3
C
CH3 H3C
H3C
H2C
H2 C
CH2 CH H2C CH3
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