Download Pre-lab 2: Naming and Modeling Organic Compounds

Name:______________
Section:_____________
Pre-lab 2: Naming and Modeling Organic
Compounds
Read the background information and answer the following questions before lab.
1. Write the electron-dot formula for ethane and determine its molecular shape.
2. Write the electron-dot formula for ethene and determine its molecular shape.
3. Draw and name the three structural isomers of C5H12. (Use the back of this page if needed)
4. Draw the two geometrical isomers, trans-2-hexene and cis-2-hexene. Label which is transand which is cis-.
5. What is the IUPAC name for the following compound? CH3CHCH-OH
CH3
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Lab 2: Naming and Modeling Organic Compounds
Objective: The objectives of this experiment include naming and modeling organic compounds,
and learning the difference between alkanes, alkenes, alkynes and different functional
groups.
Background Information:
Naming Organic Compounds:
IUPAC (International Union of Pure and Applied Chemistry) has devised a formal system of
naming organic compounds. In order to employ this system you will need to memorize some of
the basics: the ten root names, suffixes, and prefixes.
The ten root names are:
meth
eth
prop
but
pent
hex
hept
oct
non
dec
The suffixes tell which type of compound it is:
ane- an alkane
ene- an alkene
yne- an alkyne
ol- an alcohol
The prefixes are for branches or alkyl groups:
methyl- -CH3
ethyl- -CH2CH3
propyl- -CH2CH2CH3
chloro- -Cl
bromo- -Br
Basic Rules for Naming:
1. Count the carbons in the longest chain or ring containing any
functional groups or double/triple bonds.
2. Use the appropriate suffix to tell the type of compound, for
example, alkane, alkene, alkyne, etc.
3. Name the branches using the –yl ending.
Figure 1.
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4. Number the carbons starting on end closest to:
For alkanes: the branch
For rings: at the carbon where the branch closest to the
beginning of the alphabet attaches,
For alkenes, alkynes and alcohols: at the end closest to the
multiple bond or –OH group.
5. If you have two or more branches they are listed in alphabetical order.
6. If you have a compound with a double bond then you have the possibility of geometrical
isomers.
Modeling Organic Compounds:
The structures of organic compounds are largely responsible for their physical and chemical
behaviors. Compounds with the same chemical formulas may have very different properties
because of the position of the atoms. A physical model can therefore provide valuable
information about the structure and interaction of compounds and it is always helpful to see the
compounds in 3-D.
When a molecular model is built, other properties of the compound can also be investigated.
The rotation of bonds is one property seen clearly by modeling. Rotation is free around single
bonds, but with double and triple bonds no rotation is possible. This makes the structures of
double and triple bonded compounds more rigid. When rotation around a single bond occurs,
several conformations are possible. Since no rotation is possible around double and triple bonds,
only one conformation is possible without breaking the bonds. The rigidity of double bonded
compounds gives rise to a type of isomers called geometrical isomers.
Geometrical isomers are named with a cis- (same side) or trans- (opposite sides) prefix. The
structures are similar except for the position of chain or branches with respect to the double
bond. Two geometrical isomers of butane are shown in Figure 2.
The first steps in constructing your models will be to draw the
electron-dot formulas for each compound and then determine its shape
using Figure 3. For a review of electron-dot formulas and shapes look
back at lab 1.
Model Structures you will build:
1. alkanes: These are saturated hydrocarbons where the carbon makes
fours single bonds with other atoms.
1. alkenes: These are unsaturated hydrocarbons containing carboncarbon double bonds with three electron groups.
2. alkynes: These are unsaturated hydrocarbons containing carboncarbon triple bonds with two electron groups.
3. ring: saturated and unsaturated hydrocarbons may form rings with the
root name cyclo-.
Figure 2.
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4. functional groups: groups bonded the compound that contain atoms other than carbon and
hydrogen. They give functionality to organic compounds. Functional groups include:
alcohols with an (-OH) group and named with an –ol suffix in place of –ane for the alkane
chain, carboxylic acids (-COOH) –oic acid, esters (-COO-) –oate, amine (-NH2) –amine, and
aldehyde (-CHO) –al.
Figure 3.
Procedure:
Data:
Naming Organic Compounds:
From the condensed structural formulas listed on the following page, draw out the expanded
structural formula for each.(include all hydrogen.) Then using the IUPAC rules, name the
organic compound.
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#
Condensed Stucture
1
CH4
2
CH3-CH2-CH3
Expanded Structure
Name
CH3CH-CH2-CHCH2CH3
CH3
3
CH2
CH3
CH3CH2
C = C
4
H
5
H
CH2CH2CH3
Cl-CH2CH2CH2-OH
Redraw 3 and 5 on your report sheet.
Draw the condensed or expanded structure for each of the following IUPAC names.
6. 3-methylhexane
7. 4-methyl-cyclopentene
8. 6-bromo-2-methyl-2-hexanol
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9. 5,5-diethyl-3-heptyne
10. 1-chloro-3-methylcyclopentane
Redraw 7, 9, and 10 on your report sheet.
Modeling Organic Compounds: Alkanes
Fill in the following chart and draw the three structural isomers for C5H12. Using a modeling kit,
construct a model for each.
# Molecular
Total #Valence Electron-Dot
IUPAC Name
3-D Structure
Formula
Electrons
Formula
11
C2H6
12
C3H8
13
C5H12
14
C5H12
15
C5H12
Redraw the three structural isomers 13, 14, and 15 on your report sheet.
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Modeling Organic Compounds: Alkenes and alkynes
Fill in the chart and build the model for each.
# Molecular Formula
Total # Valence Electron-Dot
Electrons
Formula
16
IUPAC Name 3-D Structure
C2H4
17
2-pentyne
18
cis-1,2dichloroethene
19
trans-1,2dichloroethene
Modeling Organic Compounds: Cyclic hydrocarbons
# Molecular Formula
Total # Valence Electron-Dot
Electrons
Formula
IUPAC Name
20
C6H12
cyclohexane
21
C6H6
benzene
Modeling Organic Compounds: Functional Groups
# Molecular Formula
Total # Valence Electron-Dot
Electrons
Formula
IUPAC Name
22
C2H5OH
ethanol
23
CH2O
ethanal
24
CH3COOH
Ethanoic acid
Redraw 18, 19, 21 and 24 on your report sheet.
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3-D Structure
3-D Structure
Name:_______________________
Naming and Modeling Report Sheet
Partner(s):____________________
_____________________________
Section:______________________
Naming Organic Compounds:
#
Expanded Structure
Name
3
5
Drawing the structure from the IUPAC name.
7. 4-methyl-cyclopentene
9. 5,5-diethyl-3-heptyne
10. 1-chloro-3-methylcyclopentane
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Modeling Organic Compounds: alkanes
# # of Valence Electrons Electron-Dot Formula
13
IUPAC Name
3-D Structure
14
15
Modeling Organic Compounds: Alkenes, alkynes, cyclic hydrocarbons and functional groups
#
# of Valence Electrons
Electron-Dot Formula
18
19
21
24
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IUPAC Name
3-D Structure