Download Activity 1: Chapter 1: Carbon Compounds and Chemical Bonds

Lab Workshop 1: Nomenclature of alkane and cycloalkanes
Each student work group choose a Leader (reads activity out loud, poses questions to group), Facilitator (makes sure
everyone is participating equally, directs the conversation), Recorder (takes note on discussion, learned concepts and any
conclusions), and Presenter (announces conclusions or presents activity to class).
A.
Nomenclature of Unbranched Alkanes (IUPAC System – International Union of Pure and Applied Chemistry)
Alkane = molecule consisting entirely of carbon and hydrogen atoms connected by single bonds.
Critical Thinking Question (CTQ):
1. Cross out each molecule that is not an alkane
H2
C
H3C
H2
C
H2
C
C
H2
CH3
H3C
H2
C
CH
CH3
CH3
C
C
H3C
Memorization Task 1:
NAME
methane
ethane
propane
butane
pentane
hexane
heptane
octane
nonane
decane
undecane
dodecane
tridecane
tetradecane …
eicosane
Cl
H3C
CH3
H3C
CH3
HO
H3C
CH3
Unbranched Alkanes
Structure
CH4
CH3CH3
CH3CH2CH3
CH3(CH2)2CH3
CH3(CH2)3CH3
CH3(CH2)4CH3
CH3(CH2)5CH3
CH3(CH2)6CH3
CH3(CH2)7CH3
CH3(CH2)8CH3
CH3(CH2)9CH3
CH3(CH2)10CH3
CH3(CH2)11CH3
CH3(CH2)12CH3
CH3(CH2)18CH3
# carbon atoms
1
2
3
4
5
6
7
8
9
10
11
12
13
14
20
Critical Thinking Questions:
2. Write the correct name of the unbranched alkane in CTQ1.
3. What suffix do all the names of unbranched alkanes have in common?
4.
What prefix stands for six carbons?
O
B. Nomenclature of Branched Alkanes:
Parent Chain = longest continuous carbon chain found in a branched compound.
Substituent = groups branching off the parent chain (side chain numbering always starts at the atom connected to the parent
chain);
Alkyl groups = substituent groups branching off the parent chain that consist entirely of carbon and hydrogen.
locant = the carbon number where a group branches off the parent chain (used to indicate the location of a substituent)
Critical Thinking Question (CTQ):
5. Circle the parent chain in each molecule below and name the parent chain.
6. Number the parent chain to give the substituents the lowest number possible.
CH3
H3C
CH3
CH
3
2
C
H2
1
H2
C
5
CH
7
CH3
4
CH
6
C
H2
8
CH3
Parent chain = octane
IUPAC name = 2,5,6-trimethyloctane
Memorization Task 2:
NAME
methyl
ethyl
n-propyl
isopropyl
Commonly found alkyl substituents
Structure
CH3CH3CH2CH3CH2CH2H3C
# carbon atoms
1
2
3
3
CH
H3C
n-butyl
isobutyl
CH3(CH2)2CH2H3C
CH
4
4
CH2
H3C
H2
C
sec-butyl
H3 C
H 3C
tert-butyl
CH3
4
CH
CH3
4
C
H 3C
n-pentyl
CH3(CH2)3CH2-
5
NOTE- If multiple different substituents exist on a parent chain, list them alphabetically, not including the di, tri, sec or tert
prefixes (but iso is included when alphabetizing)
7.
In the IUPAC name in CTQ6, what information do the numbers in the names convey?
8. What does the word “tri” indicate?
9. Give the IUPAC names for the remaining two molecules above.
10. Explain what is wrong with each of the following names and correct each name:
a. 4,4-dimethylpentane
b.
1,1,1-trimethylbutane
c.
2,2-methylpentane
d.
2-dimethylpentane
e.
6-ethyl-2-methyl-4pentyloctane
C. Nomenclature of Cylic Alkanes:

If a ring is present in a molecule, the ring is almost always considered the parent chain.

Use the word cyclo as a prefix before the alkane name to indicate it is a cyclic parent chain

Number the carbons that bear substituents starting with one, and number around the ring towards the closest carbon
that bears another substituent group to give all substituents lowest possible numbering.

If there are two or more substituents, use alphabetical order to determine where to start numbering.
Critical Thinking Question (CTQ):
11. Give the correct IUPAC name for the remaining three compounds below.
12. Draw the structures that correspond to the following names:
a.
3-ethylheptane
b.
1,1-diethylcyclopropane
c.
4-sec-butyl-1-isobutyl-2-methylcylcohexane
13. Mono-substituted cycloalkanes do not include the “1” locant. Thus, 1-methylcyclohexane is inaccurate.
Draw methylcyclohexane; explain why adding a locant does not add any new information.
D. Nomenclature of Alkenes:
Functional Group = the particular group of atoms in a molecule that primarily determines how the molecule will react.
Alkyl halide = a hydrocarbon having at least one halide connected to a carbon atom.
Alkene = a hydrocarbon having at least one double bond between carbon atoms.
Alkyne = a hydrocarbon having at least one triple bond between carbon atoms.
Alcohol = a hydrocarbon containing an “O-H” functional group connected to a carbon atom that bears no other substituent
but alkyl groups.
The functional group(s) in a molecule usually determine the classification of that molecule and are indicated by suffixes in
the name. The highest priority functional group determines its classification and lower priority functional groups often
become substituents, indicated with prefixes. These will be learned slowly over the semester as we study each class of
organic compounds.
Rules for IUPAC naming:
 Determine the parent chain (longest continuous chain or ring) of the molecule that includes the functional group of
highest priority. Start numbering starting at the appropriate end of the parent chain (so important substituents have
the lowest numbers).
 Number parent chain across a double or triple bond giving the bond lowest numbering unless an –OH group is
present. Then it has highest priority and must be given lowest numbering.
 drop –ane and add +ene for double bonds or +yne for triple bonds (double and triple bonds usually have the same
priority, so number them to give the lowest numbering overall).
 Indicate location by the # of the first atom of the multiple bond or the # of the carbon to which the –OH is attached.
 Indicate the location and name of substituents as prefixes giving them lowest numbering possible, arrange
alphabetically, and prefix with di, tri, tetra, if needed.
 Halides are named as substituents and have the same priority as alkyl substituents, thus, are numbered and arranged
alphabetically.
 Designate cis or trans or E or Z for double bonds when needed (we will learn this later).



Number cyclic cmpds so that C1 and C2 include the multiple bond if a double or triple bond is present. If an –OH
group is present, then start numbering at the C bearing the OH and give the double bonded carbon atoms the lowest
number possible.
If treated as substituents, CH2=CH— and CH2=CH-CH2— are called vinyl (or ethenyl) and allyl groups (or 2propenyl), respectively.
Side chains containing an alkene or alkyne are indicated as prefixes by dropping the “e” and adding “yl” like alkyl
groups (ethenyl) or (3-butynyl) [HC≡CCH2CH2----].
Always number the parent chain to give the functional group of highest priority the lowest number possible, before
considering substituents.
Critical Thinking Question (CTQ), alkenes:
H2C
Br
H2
C
H
C
CH
CH3
CH3
Cl
3-methyl-1-pentene
14. Why is the “1” locant needed in the name of the first compound above?
15. How do you know that this compound has a double bond from its IUPAC name?
16. What functional group class does it belong to?
17. Give the IUPAC names to the remaining four compounds.
E. Nomenclature of Alkene Stereoisomers (E/Z and trans/cis)
Stereoisomer = compounds with the same molecular formula that differ only in the arrangement of their atoms in space.
(Free rotation around double bonds cannot occur unless the double bond is broken and reformed.)
(Cyclic alkenes of less than 7 carbons are always cis due to the size of the ring and do not have a cis
prefix.)
H
CH3
C
H3C
H
H
C
C
H
H3C
C
CH3
Critical Thinking Question (CTQ):
18. Write the molecular formula for each of the compounds above.
19. Does the name 2-butene indicate which of the stereoisomers above is being referred to?
20. To indicate the difference between alkenes that have 2 substituents across a double bond, use the
prefix trans (across the double bond relative to each other) or cis (same side of the double bond to
each other). Thus, the correct IUPAC names for the compounds above are cis-2-butene and trans-2butene.
21. Add cis or trans where needed to the IUPAC names in the alkene CTQ question above.
When more than 2 substituents exist around a double bond, cis and trans can no longer accurately describe the
stereoisomers and a different systems is used, the Cahn-Ingold-Prelog convention of E and Z. This system can also be
used for alkenes with only 2 substituents. It will be discussed when we cover the chapter on Alkenes and Alkynes
later in the semester.
F. Nomenclature of Alkynes (use IUPAC rules indicated in Section D above):
Critical Thinking Question (CTQ), alkynes:
Br
Cl
3-bromo-4-isopropyl-7-methyl-1-octen-5-yne
22. Halides are always substituents and are named by dropping the –ine from the element name (bromine)
and adding the letter “o”. list the substituent names of the following halides: “F,” “Cl,” and “I.”
23. Why is the parent chain numbered from left to right instead of right to left in the example above?
24. Why is the 5 locant placed in front of the -yne suffix, instead of by the 1 locant? (i.e., 4-isopropyl-3,7-
dimethyl-1,5-octenyne)?
25. Note: the letter “e” is always dropped off the “ene” suffix before adding “yne” so that 2 vowels are
not together if the locant is ignored.
26. Write the IUPAC names for the remaining compounds above.
G. Nomenclature of Alcohols:
Critical Thinking Question (CTQ), alcohols (use IUPAC rules indicated in Section D above):
OH
OH
Br
2,4-cyclohexadienol
OH
27. Why doesn’t the first alcohol above have a locant in front of the “ol”?
28. Should there be a locant in front of the other alcohol suffixes shown above? Why?
29. Write the IUPAC names for the remaining compounds above.
30. Draw the following compounds:
a. 2-methyl-2-heptene
b. 5-butyl-6-isopropyl-5-decene
c. 1,1,1-trifluoro-2-pentanol
d. octa-1,3,5,7-tetrayne
e. 1-chloro-2-(chloromethyl)cyclohexane
f.
6-bromo-5-chlorocyclohex-2-enol
Assignment Finish this packet if you did not do so in lab.
PRE-LAB QUESTION: ANSWER ON THIS SHEET OF PAPER
1. The presence of functional groups in molecules determines how they are classified, and thus affects how
they are named. Explain what a functional group is and why it is a valuable piece of information to have
about a molecule.