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Class Section:
Lab – Molecular Models
Objective: To demonstrate what functional groups look like and how they react within organic chemicals.
Materials:
5 Black, Carbon Atoms
8 White, Hydrogen Atoms
5 Red, Oxygen Atoms
9 Green, Nitrogen Atoms
22 Bonding Tubes, 2.5 cm
Hydrocarbons: Hydrocarbons are molecules made of just hydrogen and carbon. Carbon
H
has four valence (bonding) electrons and can therefore make four covalent bonds. Hydrogen
has one valence electron and therefore can make only one bond. The simplest hydrocarbon is
methane, CH4, one carbon bonded to four hydrogens. It can also be drawn as to the right.
Use your molecular models to make a methane molecule. The white connectors represent
one covalent bond, two electrons shared by two atoms.
H
H
H
C
H
C
H
H
C
H
H
The next more complex hydrocarbon is ethane, C2H6. Use your model set to make an ethane
H molecule.
Next comes propane C3H8 (just like you use in a camp stove!). Use your model set to make a propane molecule.
There are two ways to construct a butane molecule, C4H10. Try to figure out what the two
ways are by experimenting with your model set. Show your teacher when you have figured
out both ways. Now draw both versions of the molecule below showing all atoms and bonds.
As hydrocarbons get bigger it is difficult to draw in all of the
carbons and hydrogens. Because of that scientist usually use a
shorthand way of representing this type of molecule. They just
draw in the bonds between carbon atoms and assume that the
hydrogens are in the places they usually are. For example the next more complex hydrocarbon is pentane, C5H12 and
is usually represented by the figure shown below.
H
Meaning
-C-C-C-C-C-
or
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
Saturated?: Make a model of C2H4, a double bond is required. You just made what is
called ethene. Draw the molecule in the box to the right using the abbreviated form (not
showing the carbons and hydrogens) in the box to the right. Could you add more
hydrogen to the carbons if you wanted to? You could if you did not have the carbons
double bonded together and you would end up with ethane again. C2H4 is a type of
molecule called an “unsaturated” hydrocarbon because it could hold more hydrogen. A good way to remember this is
to think of cleaning up spilled water with a rag. After the rag is saturated it can’t hold any more of the spilled water.
Go ahead and add in the extra hydrogens that can fit with these two carbons. . You have just “hydrogenated” your
molecule. Where have you seen the term “saturated” before? How about “partially hydrogenated”? If you have not
heard of them make sure you talk to someone who has to find out about them.
Alcohols: are hydrocarbons with hydroxyl (OH) groups attached to them. Make a model of
the most simple, methanol, CH3OH. Oxygens are red spheres. Make ethanol, C2H5OH the kind
of alcohol that people drink. Make two models of propanol, C3H7OH that are different from
each other and show them to your teacher in the box to the
left. Now draw structural formulas of the two types of
alcohol to the right. The one with the hydroxyl group on
the middle carbon is called isopropyl alcohol, or commonly “rubbing” alcohol.
Ethers: Sometimes oxygen is found in the middle of a carbon chain. This is
called an ether. Make methyl methyl ether, CH3OCH3.
H
H
O
C
H
C
Carboxylic Acids: Sometimes organic (made of carbon,
OH
hydrogen and oxygen) compounds can be acidic or basic.
Carboxylic acids can easily lose a hydrogen ion when dissolved in
water. Make ethanoic acid, CH3COOH, the simplest carboxylic
acid and show it to your teacher.
Amino Acids: these are organic compounds that have a carboxyl group (COOH)
and an amine group (NH2) attached to them. Amino Acids get hooked together to
form proteins. Make 2 Alanines, NH2CHCOOHCH3, one of the most simple amino
acids. Make one part at a time and assemble them into the whole (first the NH2, then
the CH, then the COOH, then the CH3, and then put them together in the only way
possible). Notice the pattern of the “backbone” of the molecule. What is the pattern
you observed? _________________________________ Draw your molecule in the box to the left. Now make
another Alanine.
Amino acids can join together by making what is called a “peptide bond”. Remove the OH from the carboxyl group
of one amino acid and one of the Hs from the amine group of the other. Put the OH and the H together to form a
water molecule and hook the N to the C with a new bond. Show your teacher when you have this finished creating
your “dipeptide”. When you have three or more amino acids hooked together it is called a “polypeptide” or a
“protein”. One of the smallest proteins in the human body is insulin, which is made of 54 amino acids hooked
together by peptide bonds. Notice the pattern of the “backbone” of this “protein”. What is the pattern you observed?
_________________________________
Carbohydrates: These are ring shaped molecules most of which have the formula C6H12O6.
Make two Glucose molecules (you may have to work with other groups). Each of these
individual ring molecules is known as a “monosaccharide” or simple sugar.
Now hook your Glucose molecules together by removing an OH
group from one and an H from the other as shown in the figure to
the right. Put together the OH and H to form a water molecule.
This is called dehydration synthesis. After you have connected
your Glucose molecules together you have made a “disaccharide”
(or sugar) called maltose (like in a chocolate “malt”). Show your teacher.
Polysaccharides like starch are just a whole bunch of
monosaccharides hooked together. How do you
think we digest these large substances?
_________________________
Lipids: Lipids are made of a
glycerol molecule and three fatty acids. Construct a glycerol molecule as shown at the right. Now make three fatty
acids, one saturated, one mono-unsaturated and one polyunsaturated and hook them to your glycerol by removing a
water molecule for each. You will DEFINITELLY need to work together with another group for this one. Table 1
work with 2 and 3 with 4 and so on! What you end up with is a lipid or fat molecule. Show your teacher.
Components:
3*
+