Organic Chemistry Objectives

1. Name alkanes from the structure and given the name, be able to draw the structure.

2. Distinguish between saturated and unsaturated hydrocarbons.

3. Describe the structures of alkenes and alkynes.

4. Name alkenes and alkynes from their structure and given the name, be able to draw the structure.

5. Describe the properties of alkanes, alkenes and alkynes.

6. Describe functional groups and give examples.

7. Describe the structures of alkanes, including branched, unbranched, and cyclic alkanes.

8. Describe polymers.

Hydrocarbons

Hydrocarbons are organic compounds.

-organic compound: carbon containing compounds with the exceptions of carbon dioxide, carbides and carbonates

-contain hydrogen and carbon

-simplest of the organic compounds

-covalent molecules

Classified as: alkanes, alkenes, alkynes, aromatics

Alkanes

alkane: hydrocarbon containing only C-C single bonds (-ane ending)

-saturated hydrocarbon: each carbon contains a

maximum of 4 single covalent bonds with other

atoms

-can be shown as straight chains, branched chains,

or cyclic chains

-follows the formula:

CnH2n+2

example: if n = 1, then C1H2(1)+2

to give CH4

Unbranched Alkanes

C-C bonds form in a straight line.

Naming Unbranched Alkanes

1. Use a prefix for the number of carbons it contains: meth- 1 C hex- 6 C eth- 2 C hept- 7 C prop- 3 C oct- 8 C but- 4 C non- 9 C pent- 5 C dec- 10 C2. Follow the prefix with the ending, -ane

Example: C8H18 is named octane

Hint: Hydrogen has nothing to do with the actual naming of the compound, except help you determine if the C-C bonds are single or multiple

Branched Alkanes

Name is derived from a straight-chain alkane by replacing one or more of the

hydrogen atoms by alkyl groups (which are substitued for one or more H’s) 1. a suffix that identifies the parent straight-chain alkane ♦count the number of C atoms in the longest continuous chain 2. a prefix that identifies the branching alkyl group and the number of the carbon atom to which it is attached (see p 702, Table 22-2)

Naming Branched Alkanes

1. Propane will be part of this compound’s name because the longest continuous chain has three carbons.

2. Two methyl branches are present, both on the second carbon.

♦when more than one branch of the same kind is shown, use the Greek prefixes (mono-, di-, etc.)

♦number each substituted group using the number of the carbon it is attached to (in this case, C #2)

Naming Branched Alkanes

3. What do we have?

- propane as the parent chain

- two methyl groups on the second

carbon

4. The name is:

2,2-dimethylpropane

Branched alkanes can become very complicated very quickly.

Naming Branched Alkanes

We will work through the example on p 704 of you textbook.

Do the practice problems on p 705 # 1-2 all.

Cyclic Alkanes

cycloalkane: alkanes where the carbon atoms are arranged in a ring (cyclic) structure

-contain minimum of 3 carbons

Use the same rules for naming straight-chain alkanes, but with a few modifications:

-the ring is the parent chain

Naming Cyclic Alkanes

1. Count the number of carbons and name as a

straight-chain alkane

2. Once named, place the prefix, cyclo- in front

Naming Cyclic Alkanes

Cyclic alkanes, like branched alkanes, can contain substituent groups, with each group attached being numbered with the lowest possible set of numbers

♦ if there is only one substituted group, you do not

need to number it

http://en.wikibooks.org/wiki/Image:Substituted_cyclohexane_samples1.png

Naming Cycloalkanes

We will work through the example on p 707.

Complete practice problems #10-11 on p 708

Properties of Alkanes

1. In general, the more carbons present in a straight-chain alkane, the higher its melting and boiling points.

2. They are relative unreactive.3. Because alkanes don’t have any polar bonds, they

will dissolve only those organic compounds that are nonpolar or that have low polarity, such as oils and waxes.

4. Are immiscible in water because they are nonpolar.

5. Readily undergo combustion in oxygen

Alkenes

unsaturated hydrocarbon: contains one or more double or triple bonds between carbon atoms

-does not have a maximum number of H

alkene: has at least one double bond between carbon atoms

-cannot have a one carbon alkene because you must

have at least 2 carbons for a double bond to occur

-alkenes with one double bond have twice as many

hydrogens as carbons, as shown in the formula

CnH2n

-look at Table 22-4 on page 711

Naming Alkenes

Alkenes are named in much the same way as alkanes, except we change the –ane ending to –ene

-examples: ethane becomes ethene

H2C=CH2

propane becomes propene

H2C=CH-CH3

-if there are more than 4 carbons, you must state the

location of the double bond using the lowest number

possible

C=C-C-C is 1-butene (not 3-butene)

C-C=C-C is 2-butene

Naming Cyclic AlkenesWhen you name cyclic alkenes, carbon number 1 must be attached to the double bond -example: cyclopentene (not 1-cyclopentene, since the 1 is assumed)

-example: 1,3-dimethylcyclopentene

What if the alkene is branched?

Naming Branched Alkenes

You name branched alkenes like branched alkanes with 2 differences:

-parent chain is always the longest chain that includes

the double bond, even if it is not the longest chain of

C atoms

-the position of the double bond, not the branches,

that determines how the parent chain is numbered

CH3

Example: CH2=C-CH2-CH3

2-methylbutene

Lets look at the example on p 713

Naming Alkenes Practice

P 714 # 18

P 716 # 21 b & d

More Alkane & Alkene Practice

P 732-733 # 61-65, 66ab, 67

Properties & Uses of Alkenes

Properties

1. Nonpolar, making them insoluble in water

2. Relatively low melting and boiling points

3. Fairly reactive (electron density around double bond)

Uses

1. Making plastic bags/jugs (polyethylene)

2. Ripening fruit (ethylene, or ethene-fat soluble hormone)

3. Making rubber (different alkenes)

4. aromatics/scents

Alkynes

Another group of unsaturated hydrocarbons are alkynes.

alkyne: contains one or more C-C triple bonds

-must have at least 2 carbons

-are named using the same rules as naming alkenes, except with the ending –yne instead of –ene

Properties of Alkynes

1. Similar chemical and physical properties as alkenes, though tend to be more reactive because of the high area of electron density on the triple bond

-will burn at temp >3000oC when in the presence of O2

Uses of Alkynes• Acetylene (ethyne) torches in welding• As a reagent in the manufacture of plastics and

other organic industrial chemicals

Practice

P 716 # 21a, p 733 # 66c

Functional Groups

Objectives:1. Describe a functional group and give

examples.

You have learned that there are thousands of different hydrocarbons because carbon atoms can link together and form straight, branched, and cyclic compounds.

However, carbon can also bond with atoms other than hydrogen or other carbon compounds; the most common are: O, N, F, Cl, Br, I, S and P

functional group: an atom or group of atoms that reacts in a certain way in an organic molecule.

•the addition of a functional group produces a

compound with different physical and chemical

properties than the parent hydrocarbon.

•there are several important functional groups you

need to know (see page 738, Table 23.1) and the

following:

1. phosphate -PO4

2. sulfhydryl -SH

*functional groups change the shape of a hydrocarbon molecule