Chapter 6
Organic Chemistry
Section 1 Section 2 Section 3 Section 4
Section 5 Section 6 Section 7 Section 8
Part I: Organic Compounds: Alkanes
 SECTION
6.1 Carbon: The Element of
Organic Compounds |
1. All organic compounds have one characteristic in common, they contain carbon.
Name the element that all organic compounds contain.
2. Due to the fact that all organic compounds contain carbon, organic chemistry is the study of carbon-containing compounds.
_________ chemistry is the study of carbon-containing compounds.
3. Inorganic chemistry can be defined as the study of individual elements and all noncarbon compounds. A very few carbon-containing substances are included in inorganic chemistry, such as the carbonates and bicarbonates, carbon dioxide and elemental carbon.
Classify the following compounds as organic or inorganic:
a) KCl
b) CaSO4
c) C6H8O6
d) NaHCO3
e) diamond (pure carbon)
|
SECTION
6.2 Organic and Inorganic
Compounds Compared |
4. Approximately 250,000 inorganic compounds have been identified, while there are more than six million known organic compounds.
Inorganic chemistry has (more/fewer) known compounds to study than does organic chemistry.
5. In Table 6.1 note that the normal physical state of organic compounds includes gas, liquids, or solids with low melting points. However, inorganic compounds are typically solids with very high melting points.
Because there are generally (weak/strong) forces acting between molecules, the melting points of most organic substances are low.
6. Other important distinguishing properties between organic and inorganic compounds in Table 6.1 include: their bonding within molecules, their flammability and their solubility in water.
Determine whether each of the following statements is describing organic or inorganic compounds.
a) These compounds usually form bonds between “+” and "-" charged ions within molecules.
b) These compounds are often quite flammable.
c) These compounds generally have nonpolar bonds, making them insoluble in water.
Check Answers
|
SECTION
6.3 Bonding Characteristics
and Isomerism |
7. There is such a large number of organic compounds for a couple of reasons: first, the bonding characteristics of carbon atoms and second, the isomerism of carbon-containing compounds.
Introducing the Players
Click to Enlarge
In this chapter we'll be working with three kinds of atoms - carbon, hydrogen and oxygen. (Figure above). Notice the black carbon atom has 4 pegs on it arranged in a tetrahedral. This is because carbon atoms can share 4 electrons with other atoms to complete its octet. The red oxygen atoms require 2 electrons to complete its octet, that's why there are 2 pegs. The white hydrogen atoms only need to share one electron; hence, one peg. The green straws represent a covalent bond consisting of 2 shared electrons. For our use, the carbon atoms must always have 4 bonds attached to them, the oxygen atoms must have 2 bonds attached to them, and the hydrogens must have one bond attached to them.
Connect the dots, or Tinker Toys 101
Connect 4 carbon atoms together as shown in the following picture:
Click to Enlarge
This is referred to as a carbon skeleton because only the carbon atoms are shown and not any other attached atoms. This carbon chain can be represented as:
But it is usually represented as:
C-C-C-C
A) Bonding characteristics of carbon and isomerism of carbon-containing molecules are the reasons for the extremely large number of ________ compounds.
B) Each carbon atom has _____ bonds attached to it in an organic molecule.
8. Isomerism is a property that simply means two compounds have the same molecular formula but have their atoms arranged differently in structures.
When two compounds have different structural arrangements of atoms and yet their molecular formulas are the same, the property of ________ is being demonstrated.
9. Structural isomers are one type of isomerism where the compounds have the same molecular formula, but the atoms are bonded together in different patterns.
Structural Isomers, The Mix 'em up Boys
Construct the molecule above as shown in figure 1 below:
Fig 1
Click to Enlarge
Structural isomers are basically new molecules that can be built from the same atoms that make up the original molecule. Build two structural isomers for the molecule above as show in Figure 2 and Figure 3.
Click to
Enlarge
Fig 2 Fig 3
These molecules can be represented as:
 |
 |
Is the molecule shown in Figure 4 another different structural isomer of the original molecule?
Fig 4
Click to Enlarge
No, this is not a different structural isomer. Is is the same molecule that is shown in Figure 2 above, it has just been flipped over.
Which of the structures below represents a structural isomer of the compound shown (choose all that apply):
|
SECTION
6.4 Functional Groups – The
Organization of Organic Chemistry |
10. Organic compounds are classified into families by functional groups, unique combinations of atoms, or structural features.
________ ________are one way of distinguishing one family of organic compounds from another.
11. Structural formulas can be written in two formats. In expanded structural formulas all the covalent bonds in the molecule are shown. Whereas, in condensed structural formulas only specific bonds are shown (see Example 6.2).
Condensed Formulas and Lazy Chemists
Build the 4 carbon molecule shown in Figure 1.
Fig 1 Click to Enlarge
We can represent this molecule as:
This is the expanded formula for this molecule. As you can see, it is cumbersome to draw out. Being lazy, chemists have developed short-hand (condensed) ways of representing the same molecule. The most common way would be:
CH3CH2CH2CH3
This tells us that we have a 4 carbon chain with a hydrogen atom on each of the "blank bonds" as shown in figure 2. The condensed formula tells us that the first carbon atom of the chain has 3 hydrogens attached to it, the second has 2 hydrogens attached, etc.
Fig 2 Click to Enlarge
A very lazy chemist would represent the molecule as C4H10, which basically deconstructs the entire molecule and doesn't give us any information on how the atoms are actually put together (figure 3).
Fig 3 Click to Enlarge
Identify each of the following as an expanded or a condensed structural formula:
a)
b) 
c)
Check Answers
|
SECTION
6.5 Alkane Structure |
12. The simplest of all organic compounds are hydrocarbons which contain only hydrogen and carbon atoms.
________ are organic compounds that contain only hydrogen and carbon.
13. Hydrocarbons in which every carbon atom is bonded to four other atoms by single bonds are known as saturated hydrocarbons, or alkanes (see Figure 6.2).
How do you say "I'm Full"?
Fig 1
Click to Enlarge
Construct the carbon skeleton shown in figure 1. This carbon skeleton could be represented by the structural formulas:
Now fill in the "blank bond" with hydrogen atoms to get figure 2.
Fig 2
Click to Enlarge
A) How would you represent this molecule using condensed structural formulas?
B) Is this compound a saturated hydrocarbon?
Identify the alkanes (saturated hydrocarbons) in the diagrams below:
a)
b)
c)
14. The general formula used to represent alkanes is CnH2n+2 where “n” represents the number of carbon atoms in the molecule.
a) Using the formula given above, how many hydrogen atoms would there be in an alkane molecule containing four carbon atoms? Write the molecular formula for this four-carbon alkane.
b) How many hydrogen atoms are needed to complete the following structure?
15. “Normal alkanes” refer to those alkanes in which all carbon atoms are lined up in one continuous chain. In “branched alkanes”, at least one carbon is not part of the continuous chain.
Identify each of the following as a “normal” or “branched” alkane.
a) 
b) CH3-CH2-CH3
c)
|
SECTION
6.6 Conformations of Alkanes |
16. The single bonds within an alkane are capable of rotating, much like a wheel rotates on its axle. Due to this rotational ability, molecules can exist in many different orientations, called conformations (see Figures 6.7 and 6.8).
The Twists and Turns of Conformations
C-C-C-C-C-C-C
Make the 7 carbon chain represented above and shown in figure 1.
Fig 1
Click to Enlarge
Notice the bonds linking the carbon atoms allow the chain to freely rotate and twist. If we twist the chain 180o at the bond where the arrow is located, we get figure 2.
Fig 2
Click to Enlarge
Which can be represented
as:
By twisting the bonds some more, we can make the molecule look like figure 3.
Fig 3
Click to Enlarge
Which can be represented
as:
These are different conformations of the same 7 carbon molecules. By playing around with your model, you can see that many conformations of this model can be made, including:
The main thing is that we always have the same 7 carbon atoms attached to each other in a continuous chain. Conformations will become very important when naming organic compounds.
a) Alkane molecules can take on different ________ or orientations in space due to the ability of single bonds to rotate.
b) Which of the following are different conformations of butane, C-C-C-C?
1)
2)
3)
|
SECTION
6.7 Alkane Nomenclature |
17. Naming organic compounds using a systematic (IUPAC) approach can be fun. It’s kind of like a code game. Each name contains a suffix which is unique to the functional group or family of the compound. The suffix or ending that signifies the alkane family is “-ane”.
When naming organic compounds, what ending is used to denote the alkane family?
18. The root of organic compound names comes from the number of carbons that are in the longest chain. The roots for the first 10 normal hydrocarbons are: C1 = meth-, C2 = eth-, C3 = prop-, C4 = but-, C5 = pent-, C6 = hex-, C7 = hept-, C8 = oct-, C9 = non-, C10 = dec-. The root and suffix can then be together to name normal hydrocarbons. For example, an alkane with four carbons would be called butane (see Table 6.3).
A six carbon normal alkane would have the name of ________.
3) CH2=CH-CH3
2) 
3) 
2. CH3CH2CH2-NH2
3. CH3CH2CH2-OH
