Carboxylic acids
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Carboxylic Acids. Carboxyl Group. Carboxylic acids contain the carboxyl group on carbon 1. O  CH 3 — C — OH = CH 3 — COOH carboxyl group. Naming Carboxylic Acids. Formula IUPAC Common alkan -oic acid prefix – ic acid HCOOH methanoic acid formic acid

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Carboxylic Acids

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Carboxylic acids

Carboxylic Acids


Carboxyl group

Carboxyl Group

Carboxylic acids contain the carboxyl group on carbon 1.

O



CH3 —C—OH = CH3—COOH

carboxyl group


Naming carboxylic acids

Naming Carboxylic Acids

Formula IUPAC Common

alkan -oic acid prefix – ic acid

HCOOH methanoic acid formic acid

CH3COOH ethanoic acid acetic acid

CH3CH2COOH propanoic acid propionic acid

CH3CH2CH2COOH butanoic acid butyric acid


Carboxylic acids1

Carboxylic Acids

  • Abundant and widely distributed in nature, many having a Greek or Latin word describing their origin

    • acetic acid (ethanoic acid) from acetum, meaning vinegar

    • many that were isolated from fats are called fatty acids

  • Examples on page 249


Naming rules

Naming Rules

  • Identify longest chain

  • (IUPAC) Number carboxyl carbon as 1

  • (Common) Assign , ,  to carbon atoms adjacent to carboxyl carbon

    CH3

    |

    CH3 —CH—CH2 —COOH

    IUPAC 3-methylbutanoic acid

    Common -methylbutryic acid


Learning check

Learning Check

Give IUPAC and common names:

A. CH3COOH

CH3

|

B. CH3CHCOOH


Solution

Solution

A. CH3COOH

ethanoic acid; acetic acid

CH3

|

B. CH3CHCOOH

2-methylpropanoic acid;

-methylpropionic acid


Properties

Properties

  • Carboxylic acids are weak acids

    CH3COOH + H2O CH3COO– + H3O+

  • Neutralized by a base

    CH3COOH + NaOH CH3COO– Na+ + H2O


Esters

Esters

In an ester, the H in the carboxyl group is replaced with an alkyl group

O



CH3 —C—O —CH3 = CH3—COO —CH3

ester group


Esters1

Esters

  • Although polar, they do not form hydrogen bonds (reason: there is no hydrogen bonded to a highly electronegative atom!)

    • thus, much lower b.p. than the hydrogen-bonded carboxylic acids they came from


Esters in plants

Esters in Plants

Esters give flowers and fruits their pleasant fragances and flavors.


Esters2

Esters

  • Can be prepared from a carboxylic acid and an alcohol; usually a trace of mineral acid added as catalyst (because acids are dehydrating agents)

  • Note equation on bottom p. 345


Esterification

Esterification

  • Reaction of a carboxylic acid and alcohol

  • Acid catalyst

    O

    H+

    CH3 —C—OH + HO—CH2CH3

    O

    

    CH3 —C—O—CH2CH3 +H2O


Esters3

Esters

  • Naming? It has 2 words:

    • 1st: alkyl attached to single bonded oxygen from alcohol

    • 2nd: take the acid name, remove the -ic acid, add -ate

  • example on bottom p. 345


Naming esters

Naming Esters

  • Name the alkyl from the alcohol –O-

  • Name the acid with the C=O with –ate

    acidalcohol

    O

     methyl

    CH3 —C—O —CH3

    Ethanoate methyl ethanoate (IUPAC)

    (acetate)methyl acetate (common)


Some esters and their names

Some Esters and Their Names

Flavor/Odor

Raspberries

HCOOCH2CH3ethyl methanoate (IUPAC)

ethyl formate (common)

Pineapples

CH3CH2CH2 COOCH2CH3

ethyl butanoate (IUPAC)

ethyl butyrate (common)


Learning check1

Learning Check

Give the IUPAC and common names of the following compound, which is responsible for the flavor and odor of pears.

O



CH3 —C—O —CH2CH2CH3


Solution1

Solution

O

 propyl

CH3 —C—O —CH2CH2CH3

propyl ethanoate (IUPAC)

propyl acetate (common)


Learning check2

Learning Check

Draw the structure of the following compounds:

  • 3-bromobutanoic acid

  • Ethyl propionoate


Solution2

Solution

A. 3-bromobutanoic acid

Br

|

CH3CHCH2COOH

B.Ethyl propionoate

O



CH3 CH2 COCH2CH3 CH3CH2COOCH2CH3


Hydrolysis

Hydrolysis

  • Esters react with water and acid catalyst

  • Split into carboxylic acid and alcohol

    O

     H+

    H—C—O—CH2CH3 +H2O

    O

    

    H—C—OH + HO—CH2CH3


Saponification

Saponification

  • Esters react with a bases

  • Produce the salt of the carboxylic acid and alcohol

    O

    

    CH3C—OCH2CH3 + NaOH

    O

    

    CH3C—O– Na++ HOCH2CH3

    salt of carboxylic acid


Learning check3

Learning Check

Write the equation for the reaction of propionic acid and methyl alcohol in the presence of an acid catalyst.


Solution3

Solution

O

 H+

CH3CH2COH + HOCH3

O



CH3CH2COCH3 + H2O


Learning check4

Learning Check

What are the organic products when methylacetate reacts with

A. Water and an acid catalyst?

B. KOH?


Solution4

Solution

A.

O



CH3COH + HOCH3

O



B. CH3CO– K+ + HOCH3


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