AP Chemistry
Organic Chemistry Lab
Text Reference: Brown, LeMay, Bursten, and Murphy, The Central Science Chapter 25
This molecular model-building lab is designed to help you develop a mental model that
gives a three-dimensional image to two-dimensional Lewis structures that you draw on
paper. It will also help you get a better picture of the different kinds of isomers that are
possible with some molecular formulas.
Prelab Assignment:
1.
2.
3.
4.
5.
Distinguish between molecular and structural formulas.
What is the meaning of the term isomer?
Why should the properties of structural isomers differ?
Distinguish between geometric and structural isomers?
When is a carbon chiral? What hybridization does a chiral carbon have? What effect
does being chiral have on the molecule?
Procedure:
1. Sketch the Lewis structure, then build the model of the molecules. Indicate if they
are 3-dimensional, 2-dimensional or 1-dimensional in shape.
a.
b.
c.
d.
e.
f.
g.
h.
methane
ethane
ethene
ethyne
cyclopentene
1-propanol
2-propanol
NH3
2. Name each of the following organic compounds, then draw the structural formulas.
Show how many different isomers are possible with each one and name them.
a. C6H12 & C6H14
b. C4H9OH & C5H11OH
c. C2H4(OH)2 & C3H5(OH)3
d. C2H6O & C3H6O
3. Draw the Lewis structure, then build the model of the molecules. If they are chiral
label which carbon is chiral.
a.
b.
c.
d.
e.
CHBrClF
2-butanol
2-[4-(2-methylpropyl)phenyl]propanoic acid
2-(2-Propyl)-5-methyl-1-cyclohexanol
2-hydroxypropanoic acid (lactic acid)
4. Functional groups are a combination of atoms that behave as a unit and change the
character of an alkane, alkene, or benzene ring. For the following compounds: (1) list
1
Rev: 25 Oct 2010
AP Chemistry
the functional group(s) and class of the compound, (2) use the model kit to determine
the structure of the molecule, and (3) draw the structure/isomers of each compound.
a. Formaldehyde
b. Dimethyl amine
c. Ethyl acetate
d. Butanol (butyl alcohol), C4H10O
e. Thymol, C10H14O
f. Diethyl ether, C4H10O
g. Diethyl amine, C4H11N
h. Acetone, C3H6O
i. Acetic Acid, C2H4O2
j. Ethanal
2
Rev: 25 Oct 2010
AP Chemistry
Teacher Notes:
Have model kits for each student and extra parts for the more complicated molecules.
Prelab Assignment:
1. Distinguish between molecular and structural formulas.
Molecular formulas show the number and type of atoms that form a compound. The
Structural formula shows how the atoms are bonded to one another. A molecular
formula may have multiple structural formulas.
2. What is the meaning of the term isomer?
Isomers have the same molecular formula, but different structural formulas. Two or
more compounds that have the same composition, but a different arrangement of
atoms.
3. Why should the properties of structural isomers differ?
The properties will be different because the different arrangement of atoms gives the
compounds different molecular interactions so they do not behave in the same
manner.
4. Distinguish between geometric and structural isomers?
Geometric isomers have the same molecular formula and the same groups bonded to
one another, but differ in the spatial arrangement of these groups. Structural isomers
have the same molecular formula, but not the same groups or spatial arrangement.
5. When is a carbon chiral? What hybridization does a chiral carbon have? What
effect does being chiral have on the molecule?
A chiral carbon is one where the molecule if not superimposable on their mirror
image. A chiral carbon has four different groups attached. The hybridization of a
chiral carbon must be sp3. The molecule is an optical isomer, it rotates polarized
light. The chiral molecules may have different biological behaviors.
Procedure:
1. Sketch the Lewis structure, then build the model of the molecules. Indicate if they
are 3-dimensional, 2-dimensional or 1-dimensional in shape.
a. Methane
3-Dimensional
3
Rev: 25 Oct 2010
AP Chemistry
b. Ethane
3-Dimensional
c. Ethene
2-Dimensional
d. Ethyne
1-Dimensional
e. Cyclopentene (C5H8)
3-Dimensional
f. 1-propanol
3-Dimensional
4
Rev: 25 Oct 2010
AP Chemistry
g. 2-propanol
3-Dimensional
h. NH3
3-Dimensional
2. Name each of the following organic compounds, then draw the structural
formulas. Show how many different isomers are possible with each one and
name them.
a. C6H12 & C6H14
C6H12 Isomers
cyclohexane
5
Rev: 25 Oct 2010
AP Chemistry
C6H14 Isomers
6
Rev: 25 Oct 2010
AP Chemistry
b. C4H9OH & C5H11OH
C4H9OH Isomers
1-butanol
2-butanol
2-methyl-1-propanol
2-methy-2-propanol
C5H11OH Isomers
1-pentanol
7
Rev: 25 Oct 2010
AP Chemistry
2-pentanol
3-pentanol
2-methyl-1-butanol
3-methyl-1-butanol
2-methyl-2-butanol
8
Rev: 25 Oct 2010
AP Chemistry
3-methyl-2-butanol or 2-methyl-3-butanol
2,2-dimethyl-1-propanol
c. C2H4(OH)2 & C3H5(OH)3
C2H4(OH)2 (ethylene glycol)
C3H5(OH)3 (glycerin)
d. C2H6O & C3H6O
C2H6O Isomers
ethanol
9
Rev: 25 Oct 2010
AP Chemistry
Dimethyl ether
C3H6O Isomers
1. Draw the Lewis structure, then build the model of the molecules. If they are chiral
label which carbon is chiral.
a. CHBrClF
b. 2-butanol
10
Rev: 25 Oct 2010
AP Chemistry
2-[4-(2-methylpropyl)phenyl]propanoic acid (Ibuprofen)
c.
d. 2-(2-Propyl)-5-methyl-1-cyclohexanol (menthol)
e. 2-hydroxypropanoic acid (lactic acid)
2. Functional groups are a combination of atoms that behave as a unit and change the
character of an alkane, alkene, or benzene ring. For the following compounds: (1) list
the functional group(s) and class of the compound, (2) use the model kit to determine
the structure of the molecule, and (3) draw the structure/isomers of each compound.
a. Formaldehyde CH2O
i.
ii.
Functional Groups – R-CHO
Class of compound - aldehyde
11
Rev: 25 Oct 2010
AP Chemistry
iii.
Structure/Isomers
b. Dimethyl amine
i.
Functional Groups – amine, methyl
ii.
Class of compound - amine
iii.
Structure/Isomers
c. Ethyl acetate
i.
Functional Groups – carbonyl, methyl, ethyl, ester
ii.
Class of compound - ester
iii.
Structure/Isomers
d. Butanol (butyl alcohol), C4H10O
i.
Functional Groups - hydroxyl
ii.
Class of compound - alcohol
iii.
Structure/Isomers
1-butanol (isobutanol)
2methyl 1-butanol
2-butanol
(isobutanol)
(sec-butanol)
12
Rev: 25 Oct 2010
AP Chemistry
2 methyl propan-2-ol (tertbuanol)
e. Thymol, C10H14O
i.
Functional Groups – hydroxyl (phenol), methyl, propyl
ii.
Class of compound - phenol
iii.
Structure/Isomers
f. Diethyl ether, C4H10O
i.
Functional Groups - ether
ii.
Class of compound - ether
iii.
Structure/Isomers
g. Diethyl amine, C4H11N
i.
Functional Groups - amine
ii.
Class of compound - amine
iii.
Structure/Isomers
h. Acetone, C3H6O
i.
Functional Groups - carbonyl
ii.
Class of compound - ketone
iii.
Structure/Isomers
13
Rev: 25 Oct 2010
AP Chemistry
i. Acetic Acid, C2H4O2
i.
Functional Groups - carboxyl
ii.
Class of compound – organic acid
iii.
Structure/Isomers
j. Ethanal
i.
Functional Groups - carbonyl
ii.
Class of compound - ketone
iii.
Structure/Isomers
14
Rev: 25 Oct 2010