Download Organic Compounds

LAB 7. ORGANIC COMPOUNDS:
STRUCTURE & PROPERTIES
PURPOSE: To discover physical and chemical properties of organic compounds.
To identify organic functional groups from assembled molecular models.
SAFETY CONCERNS:
Always wear safety goggles. Hydrocarbons are flammable.
Keep small model pieces away from young children who may swallow them.
HYDROCARBONS:
Hydrocarbons are compounds made primarily of carbon and hydrogen. An alkane is a
hydrocarbon containing only single bonds. An alkene contains one or more carbon-carbon
double bonds. Alkynes have one or more carbon-carbon triple bonds. Aromatic
hydrocarbons contain a circular pattern of double and single bonds where the double bonded
electrons can travel completely around the ring.
Saturated hydrocarbons contain no double bond or triple bonds. Alkanes are saturated.
Unsaturated hydrocarbons contain double or triple bonds. Alkenes, Alkynes, and Aromatic
hydrocarbons are all unsaturated.
Examples:
Alkane
Alkene
Alkyne
Aromatic
(saturated)
(unsaturated)
(unsaturated)
(unsaturated)
Propane
Propene
Propyne
Benzene
H
H H H
H C
C
C
H
H
H
H
H
C C
C H
H H
H H H
H C
C
C
H
H
H
H
C
C
C
C
C
C
H
H
H
PHYSICAL PROPERTIES:
Volatility: Because of the small difference in electronegativities between carbon (C=2.5) and
hydrogen (H=2.1), hydrocarbons are characteristically nonpolar. Since hydrocarbons do not
have partially negative or partially positive atoms there is minimal attraction between
hydrocarbon molecules. Thus, hydrocarbons require less energy to evaporate or vaporize than
do polar compounds. Small hydrocarbons require less energy to vaporize than large ones. They
are highly volatile.
Odor: The volatile nature of hydrocarbons causes them to vaporize and move through the air.
These air-borne molecules reach our noses and we smell them. Many hydrocarbons have
characteristic odors.
CH110 Lab 7. Organic Compounds (W14)
73
Solubility: The nonpolar character of hydrocarbons allows them to have minimal attraction to
other hydrocarbons but causes them to repel polar compounds such as water.
Density: Nonpolar hydrocarbons have minimal attraction to each other so hold together
loosely. They have low density. Polar compounds, on the other hand, attract each other and bind
close. Water has a lot of hydrogen bonding and is particularly dense.
CHEMICAL PROPERTIES:
Combustion: Hydrocarbons easily combust in the presence of oxygen. They are commonly
used for fuel. Wood, fuel oil, gasoline, diesel, and candle wax are all common flammable
hydrocarbons fuels.
CH4
+
methane
2O2
CO2
oxygen
carbon dioxide
+
2H2O
water
Not all hydrocarbons will react with the same amount of oxygen so when burning in a normal
atmosphere they may appear very different. Aromatic hydrocarbons, for example, burn very
dirty in that they undergo incomplete combustion and produce a lot of soot. Small hydrocarbons
and alcohols are more likely to completely combust and burn cleanly, with very little or no soot.
MOLECULAR MODELS:
Models are often used by chemists to visualize molecular structures. Structural differences
between functional groups provide reasons for differences in chemical reactivity. In preparation
for this laboratory exercise, review the sections in your text book pertaining to molecular
structure of compounds such as alkanes, alkenes, alkynes, aromatics, alcohols,
ethers, aldehydes, ketones, carboxylic acids, and esters . Be able to identify each of
these functional groups and be able to write condensed and full structural formulas for them.
Alcohols and ethers can be viewed as derivatives of water where one or both of water’s H
atoms have been replaced by a carbon group (R). The –OH group of an alcohol is called a
hydroxyl group.
Water
Alcohol
General Structure
H-O-H
Specific Example
H H
R-O-H
H C C O H
H H
Ethyl Alcohol
Ethanol
H H
H
Ether
R-O-R
H C C O C H
H H
H
Ethyl Methyl Ether
Methoxyethane
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CH110 Lab 7. Organic Compounds (W14)
Aldehydes and Ketones contain the carbonyl group. Aldehydes have one or two hydrogen
atoms attached to the carbonyl carbon. Ketones have two carbon groups bonded to the carbonyl
carbon.
General Structure
Carbonyl
Specific Example
O
C
Aldehyde
O
O
H C H
or
O
H O
H C H
H C C H
R C H
H
Ethyl aldehyde
Ethanal
Formaldehyde
Methanal
Ketone
H O H
O
H C C C H
R C R
H
H
Acetone
Propanone
Carboxylic Acids contain both the carbonyl group and the hydroxyl group; the hydroxyl
group must be bonded to the carbonyl carbon. Together the carbonyl gropu and the hydroxyl
group are called the carboxyl group.
Esters are derivatives of carboxylic acids. The hydrogen atom of the carboxyl group has been
replaced by a carbon group.
General Structure
Carboxyl
Specific Example
O
C O H
Carboxylic
Acid
O
O
H C O H
O
or
H O
H C O H
R C O H
H
Formic Acid
Methanoic Acid
O
Ester
O
H C O R
O
or
R C O R
H C C O H
H H
H C O C C H
H H
Ethyl Formate
Ethyl Methanoate
CH110 Lab 7. Organic Compounds (W14)
Acetic Acid
Ethanoic Acid
H O
H
H C C O C H
H
H
Methyl Acetate
Methyl Ethanoate
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NOTES:
PROCEDURES:
1
The beakers must have
identical surface areas so
that each of the liquids has
the same amount exposed
for evaporation.
ACTIONS:
I. PHYSICAL PROPERTIES:
A. Volatility:
1. Obtain three 50mL beakers of identical1 size. Label2 them #1, #2, #3.
2
2. Into beaker #1 put 5 mL of water.
Into beaker #2 put 5 mL of ethanol.
Into beaker #3 put 5 mL of hexane.
3. Carefully weigh each beaker from Part IA on the electronic balance 3
and record the masses on your report sheet.
Some beakers have a
white patch where labels
can be written with pencil.
Otherwise use a grease
pencil
to
clearly
distinguish your beakers.
3
4
4. Weigh each beaker again every 15 minutes and record the masses.
5. On the report sheet make a graph of the total mass lost by each
substance every 15 minutes. Draw a straight line through the graph
points to show the linear relationship for the evaporation of each
liquid. Compare to determine relative volatility.5
6.
In between beaker weight readings continue working on other parts of
the lab.
Use the same balance for
each measurement to avoid
errors.
4
Continue working
other parts of the lab
come back every
minutes to weigh
beakers in this part.
on
and
15
the
5
A
volatile
liquid
evaporates very easily.
B. Odor:
7. Waft the vapors6 of each of the 3 beakers and record your observations
on the report sheet.7
C. Solubility in Water:
8. After your mass data over 60 minutes has been collected from Part IA.
 Pour some of the water from beaker #1 into beaker #2 with the
ethanol. Swirl to mix.
 Pour the rest of the water into beaker #3 with the hexane.8 Swirl to
mix.
9. Check beakers #2 and #3 for layers.8 Using the diagrams given record
your observations about the solubility of each hydrocarbon in water.
Explain the presence of any layers formed.
Never smell a chemical
directly but instead gently
“waft” the vapors toward
your nose.
7
We are using hexane to
represent the odor of all
hydrocarbons although not
all hydrocarbons smell
exactly
the
same.
Compare
the
general
properties of the odor of
water, hydrocarbon, and
alcohol.
8
D. Density:
10. Observe beaker #3 with the water and hexane mix. Determine which
substance (water or hexane) has the greatest density. On the report
sheet label the identity of each layer.
11. Dispose of the contents of beaker #3 in a designated hydrocarbon
waste container.
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6
CH110 Lab 7. Organic Compounds (W14)
If you are not certain that
an insoluble layer is
forming or if the layers are
to small then add a couple
more mLs of water or
hexane and see if a layer
gets bigger.
II. CHEMICAL PROPERTIES:
A. Combustion (Instructor Demo):
1. Line up 3 clean and dry9 watch glasses about 6 inches apart in a fume
hood.
2. Onto watch glass #1 put 10 drops ethanol. (C2H5OH) (an alcohol)
Onto watch glass #2 put 10 drops of hexane. (C6H14) (an alkane)
Onto watch glass #3 put 10 drops toluene. (C6H5CH3) (an aromatic)10
3. Ignite each liquid with a burning wood splint and compare the colors
and types of flames produced by each hydrocarbon as they burn
together. 11
4. Record your observations.
9
The glassware must very
dry. If any water is present
your results may not be
accurate.
10
We are using toluene,
(methyl benzene) as a
representative of the family
of aromatics. It is less toxic
than benzene because it is not
as flat (planar) so therefore
does not intercollate as
readily into our spiral DNA.
11
Observe
if
the
hydrocarbons ignited rapidly
or if they were slow to ignite.
Observe if there is a “clean”
flame or a “sooty” flame.
III. MOLECULAR MODELS:
Examine the numbered models provided. Each of the models represents an
organic molecule that contains one or more oxygen containing functional
groups. In the space provided on the Report Sheet, give the information
requested for each model.
1.
12
A. Write the structural formula for this compound.
B. Enclose the carbonyl group in a rectangle and label it “carbonyl
group”.
C. Write the name of the compound class.12
D. Is this compound easily oxidized, reduced, hydrolyzed, or
esterified? 13 (circle those that apply)
E. What is the IUPAC name of this compound?13
F. What is the common name of this compound? 13
Determine the functional
group class such as alcohol,
ether, aldehyde,
ketone,
carboxylic acid, or ester.
13
You may need to consult
your text book for this
information.
2.
A.
B.
C.
D.
E.
F.
G.
Write the structural formula for this compound.
Circle and label the polar region of this compound.
Box and label the non-polar region of this compound.
Write the name of the compound class.12
Will this compound form hydrogen bonds? (Yes or No?)
Is this compound soluble in water? (Yes, No, or partially?)
Is this compound easily oxidized, reduced, hydrolyzed, or
esterified? 13 (circle those that apply)
3.
A. Write the structural formula for this compound.
B. Write the name of the compound class.12
C. Name the two classes of compounds that would result from the
hydrolysis of this compound.
CH110 Lab 7. Organic Compounds (W14)
77
4.
A. Write the structural formula for this compound.
B. Write the name of the compound class.12
C. Is this compound easily oxidized, reduced, hydrolyzed, or
esterified? 13 (circle those that apply)
D. Is this compound soluble in water? (Yes, No, or partially?)
E. What is the Common name of this compound?13
5.
A.
B.
C.
D.
Write the structural formula for this compound.
Write the name of the compound class.12
Circle the acidic hydrogen in this compound.
Is this compound a strong acid, weak acid or a neutral compound?
(circle one)
E. Is this compound soluble in water? (Yes, No, or partially?)
F. What is the IUPAC name of this compound?13
G. Write an equation showing how this compound ionizes in water.14
6.
A. Write the structural formula for this compound.
B. Write the name of the compound class.12
C. Is this compound easily oxidized, reduced, hydrolyzed, esterified,
or reactive with alcohols? 13 (circle those that apply)
D. Is this compound soluble in water? (Yes, No, or partially?)
E. Give the IUPAC name for this compound.
78
CH110 Lab 7. Organic Compounds (W14)
14
Do not use generalizations
but rather write an equation
showing the ionization of the
specific molecule in question.
LAB 7. ORGANIC COMPOUNDS:
NAME_____________
DATE______________
PRE LAB EXERCISES:
1. Draw the structural formula for each of these hydrocarbons:
Ethanol
Hexane
Toluene
Formaldehyde
2. Match the following terms with the structures they represent:
A.
1.___
Alcohol
2.___
Alkane
3.___
Alkene
F.
H
H
C C
H
CH3
B.
Alkyne
5.___
Aromatic
6.___
Aldehyde
7.___
Carboxylic Acid
C.
9.___
Ester
Ether
10.___ Ketone
_____3.
O
CH3CH2C O CH2CH3
H.
H
H C C C H
H
D.
O
CH3CH2CCH3
J.
H
H
8.___
CH3CH2CH
G.
H H H OH
H C C C C H
H H H H
4.___
O
O
CH2 CH3
H
CH3CH2C OH
H
H
E.
H H H H
H C C C C H
H H H H
K.
CH3CH2CH2OCH2CH3
The black soot is given off when certain hydrocarbons are burned because __
A. the fuel is undergoing complete combustion in the presence of oxygen.
B. carbon dioxide and water mix to give a black powder.
C. there is not enough oxygen present in the environment to combust that much fuel.
D. more than one of these.
CH110 Lab 7. Organic Compounds (W14)
79
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CH110 Lab 7. Organic Compounds (W14)
LAB 7. ORGANIC COMPOUNDS:
NAME___________________
PARTNER_________DATE___
REPORT:
I. PHYSICAL PROPERTIES:
A. Volatility:
a. Mass at Start
b. Mass lost in zero min
c. Mass at 15 minutes
d. Total g’s lost from beginning
e. Mass at 30 minutes
f. Total g’s lost from beginning
g. Mass at 45 minutes
h. Total g’s lost from beginning
i. Mass at 60 minutes
j. Total g’s lost from beginning
#1 + Water
#2 + Ethanol
#3 + Hexane
Mass in grams
Mass in grams
Mass in grams
Og
Og
Og
(a-c)
(a-c)
(a-c)
(a-e)
(a-e)
(a-e)
(a-g)
(a-g)
(a-g)
(a-i)
(a-i)
(a-i)
Mass lost by Water (#1), Ethanol (#2), and Hexane (3#)
Total
Mass
Lost
From the
Beginning
(in grams)
0
15 (a-c)
30 (a-e)
45 (a-g)
60 (a-i)
Time (in minutes)
Volatility Results Summary: Rank the substances in order of decreasing volatility.
Most volatile
>
>
A. On the given structures of ethanol label any partially
positive (+) or partially negative (-) atoms.
B. Draw a dotted line (…..) to show Hydrogen bonding
H H
H C C O H
H H
Least volatile
H H
H O C C H
H H
forming between the 2 ethanol molecules given.
Conclusion/Explanation/Analysis: Why did the three liquids behave as they did? Be specific.
Water
Ethanol
Hexane
CH110 Lab 7. Organic Compounds (W14)
81
Water
Ethanol
Hexane
An Alcohol
A Hydrocarbon
B. Odor
Explain the correlation between volatility and odor
Ethanol
Hexane
An Alcohol
A Hydrocarbon
C. Solubility
And
D. Density
Physical Properties Results Summary:
_____1.As a general rule, hydrocarbons are _____ than water.
A. more volatile
B. less volatile
C. there is no general rule
_____2.As a general rule, hydrocarbons are _____ in water and _____in other hydrocarbons.
A. soluble, soluble
C. insoluble, soluble
B. insoluble, insoluble
D. soluble, insoluble
_____3.As a general rule, most hydrocarbons are _____ than water.
A. more dense
B. less dense
C. there is no general rule
_____4.Ethanol is ___________________in water ______________.
A. soluble, because the OH is polar.
B. insoluble, because it is a mostly hydrocarbon.
II. CHEMICAL REACTIVITY:
Ethanol
Hexane
Toluene
An Alcohol
An Alkane
An Aromatic
A. Combustion
Chemical Reactivity Results Summary:
_____5.Which of the following generally give the most soot when burned?
A. Alcohols B. Alkanes
C. Aromatics
_____6.The black soot that is given off when certain hydrocarbons are burned is due to ___
A. impurities that were present in the original sample.
B. elemental carbon.
C. a mixture of carbon monoxide and carbon dioxide..
D. none of these.
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CH110 Lab 7. Organic Compounds (W14)
III. MOLECULAR MODELS:
NAME __________
Follow the procedures in the lab using the following pictures of molecular models.
Red spheres represent oxygen atoms, black spheres represent carbon atoms and white ones represent hydrogen. Short grey pegs
are carbon to carbon single bonds, short white pegs are carbon to hydrogen bonds and long grey pegs are carbon to oxygen
double bonds. In the space provided on the Report Sheet, give the name of the compound class, draw the full structural formula
of the molecule and answer questions asked about each model.
No. 1
Side View
Top View
1.
A. Structure (Complete, not condensed)
C. Class_________________________
D. Circle any of the following reactions that can easily
be performed on this compound
a) Oxidation
d) Esterification
b) Reduction
c) Hydrolysis
e) none of these
E. IUPAC Name __________________
B. Functional group (Box it)
F. Common Name _________________
____________________________________________________________________
No. 2
Side view
Top view
2.
A. Structure
D. Class _________________________
E. Hydrogen Bond? _______________
F. Water soluble? _________________
B. Polar region (circle)
C. Nonpolar region (box)
G. Circle any of the following reactions that can
easily be performed on this compound
a) Oxidation
d) Esterification
CH110 Lab 7. Organic Compounds (W14)
b) Reduction
e) none of these
c) Hydrolysis
83
____________________________________________________________________
No. 3
Side view
Top view
3.
B. Class _________________________
A. Structure
C. Acid Hydrolysis products (classes):
____________________________________
No 4
Side view
Top view
4.
A. Structure
B. Class _________________________
C. Water soluble? _________________
D. Common Name _________________
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CH110 Lab 7. Organic Compounds (W14)
No 5
Side view
Top view
5.
A. Structure
B. Class _________________________
C. Acidic Hydrogen (circle)
D. Strong acid, Weak acid, Neutral?
E. Water Soluble? __________________
F. IUPAC Name __________________
G. Equation for Ionization in water
No. 6
6.
A. Structure
Side view
Top view
B. Class _________________________
C. Circle any of the following reactions that can
easily be performed on this compound
a) Oxidation
c) Hydrolysis
e) Rxn with Alcohols
b) Reduction
d) Esterification
e) none of these
D. Water Soluble? __________________
E. IUPAC Name __________________
CH110 Lab 7. Organic Compounds (W14)
85
LAB 7. ORGANIC COMPOUNDS:
RELATED EXERCISES:
NAME_____________
1. Write balanced chemical equations to represent the following reactions:
A. Combustion of Ethanol: (Use structures not formulas for ethanol)
B. Combustion of Hexane: (Use structures not formulas for hexane)
2. Name the class of compound associated with each of the following:
A. An Anesthetic
_____________________________
B. Fragrances
_____________________________
C. Distilled Spirits _____________________________
D. Vinegar
_____________________________
3. You are on a chemical scavenger hunt. As a minimum you need to find an ester, a carboxylic acid,
and an alcohol. Go to the kitchen, bathroom, medicine cabinet, garage, grocery store etc. and find
three different items that contain the functional groups on the label. List your findings below.
Functional Group
Product
Chemical Name on the Label
Ester
Carboxylic Acid
Alcohol
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CH110 Lab 7. Organic Compounds (W14)