Chapter 14 Some Compounds with Oxygen, Sulfur or a Halogen

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Chapter 14Some Compounds with Oxygen, Sulfur or
a Halogen
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Part ISome Oxygen Containing CompoundsAlcohols,
Phenols and Ethers
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• Cases
• R1 and R2 are carbon groups Compound is an ether.

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• R1 is a carbon group and R2 is hydrogen Compound
  is an alcohol.

A special case of alcohols occurs when the carbon
group is an aromatic (benzene based). In this
case, the alcohol receives the special name of
phenol.
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Naming Alcohols

• Alcohols with one OH group are often referred
  to by common names that identify the alkyl group
  and then add the word alcohol. For example

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• IUPAC rules for naming alcohols
• Step 1 Find the longest chain containing the
  carbon to which the OH group is attached. Name
  the chain by taking the name of the corresponding
  alkane and changing the e ending by ol

The main chain contains 6 carbons. This alcohol
is therefore a hexanol.
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• Step 2 Number the carbon atoms in the main chain
  starting by the end closest to the hydroxyl (-OH)
  group. Ignore other groups for now.

6 5 4 3 2 1
Step 3 Write the name by starting with the
substituents in the usual way followed by the
location of the OH group and the parent compound
5-methyl-3-hexanol
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• Notes
• If there is more than one OH group present,
  start numbering by the end closest to a hydroxyl
  group. Insert di, tri, etc. before the -ol ending
  to indicate the number of OH groups present.

Notice that in this case we did not replace the
-e from propane!
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• Cyclic alcohols Carbon 1 is the one to which the
  OH group is attached. Number the other carbons
  following the direction that will give other
  substituents the lower sequence of numbers. It is
  not necessary to write 1 in the name of the
  alcohol to indicate the position of the OH group.

3,4-dimethyl-cyclohexanol
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Properties of Alcohols

• We can think of alcohols and ethers as
  derivatives of water in which one (alcohols) or
  two (ethers) hydrogens have been replaced by
  organic groups.
• In the case of alcohols, part of the water
  structure remains intact and we should expect
  alcohols to somewhat have similar properties than
  those of water.

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• Despite the small molecular weight of water, it
  has the highest boiling point in this series.
• Propane and ethanol have similar molecular
  weights but their boiling points are extremely
  different.

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• The unusual high B.P. of water is due to its
  ability to form hydrogen bonds.
• A hydrogen bond is formed whenever we have a
  hydrogen atom bonded to O, S, N or F.

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• Molecules with hydrogen bond capabilities usually
  can form networks of molecules. This additional
  attraction is usually responsible for the higher
  B.P. in these compounds.

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• This ability to form hydrogen bonds is preserved
  in alcohols.

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• As a consequence of its ability to form hydrogen
  bonds, alcohols have high boiling points.
• Alcohols up to 12 carbons are liquids at room
  temperature.

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• Alcohols are polar compounds. Thus, we expect
  them to be soluble in polar solvents.
• However, care must be exercised in making these
  generalizations. As the size of the organic part
  increases, the properties of alcohols become more
  hydrocarbon-like.

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• Alcohols with more than one OH group can form
  multiple hydrogen bonds. As a consequence they
  have higher boiling points and increased
  solubility in water.

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Reactions of Alcohols

• 1) Dehydration Loss of water. It requires an OH
  group an a hydrogen in an adjacent carbon. The
  product is an alkene.

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The situation is more complicated when we have
more than one H that we can extract
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Notice that there are two carbons from which we
can take the hydrogen.
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• While the addition of water to a double bond
  produced only one product according to
  Markovnikovs rule, the dehydration reaction
  produces a mixture of the above products.

However, one of the products will usually be
produced in larger amounts. This is normally
referred to as the favored or major product.
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The rule to determine which is the favored
product is as follows The alkene with more
carbons attached to the carbons of the double
bond will be produced in larger amounts.
Only one carbon group attached to the carbons of
the double bond.
Two carbon groups attached to the carbons of the
double bond.
This is the minor product
This is the favored product
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Classification of Alcohols

• Alcohols are classified as primary, secondary or
  tertiary according to the type of carbon
  (primary, secondary or tertiary) to which the OH
  group is joined to.

Primary Alcohol
Secondary Alcohol
Tertiary Alcohol
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• Oxidation From the point of view of organic
  compounds we will call an oxidation any rxn. that
  increases the number of bonds to oxygen.
• Depending of the type of alcohol (primary,
  secondary or tertiary) involved in an oxidation
  and the conditions of the rxn., the products can
  be either aldehydes, ketones or carboxylic acids.

Aldehyde Carboxylic Acid
Ketone
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• Primary Alcohols In carefully controlled
  conditions the product is an aldehyde. If there
  is an excess of the oxidizing agent the reaction
  produces a carboxylic acid. Look for the word
  excess to determine the correct product.

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• Secondary Alcohols The product is a ketone.

• Tertiary Alcohols Do not react