Organic Chemistry : Identifying Carbonyl Compounds

Study concepts, example questions & explanations for Organic Chemistry

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Example Questions

Example Question #1 : Identifying Carbonyl Compounds

Identify the given organic functional group.

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Possible Answers:

Ketone

Aldehyde

Acid anhydride

Ester

Carboxylic acid

Correct answer:

Aldehyde

Explanation:

Aldehydes are carbonyls with one R-group and one hydrogen attached to the carbonyl carbon.

Example Question #11 : Organic Functional Groups

Identify the given organic functional group.

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Possible Answers:

Acetal

Aldehyde

Ketone

Carboxylic acid

Ester

Correct answer:

Ketone

Explanation:

Ketones are carbonyls with two R-groups attached the the carbonyl carbon.

Example Question #12 : Organic Functional Groups

Identify the given organic functional group.

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Possible Answers:

Acid halide

Amide

Acid anhydride

Carboxylic acid

Ester

Correct answer:

Acid halide

Explanation:

This is an acid halide, were X is any halogen (group VII). They are the most reactive of all the carboxylic acid derivatives.

Example Question #2 : Identifying Carbonyl Compounds

Identify the given organic functional group.

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Possible Answers:

Ester

Acid anhydride

Ketone

Aldehyde

Carboxylic acid

Correct answer:

Carboxylic acid

Explanation:

Carboxylic acids are composed of one R goup and a hydroxy group bound to the carbonyl carbon. The hydroxyl group gives the molecule acidic properties.

Example Question #3 : Identifying Carbonyl Compounds

Identify the given organic functional group.

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Possible Answers:

Aldehyde

Acetal

Acid anhydride

Hemiketal

Ester

Correct answer:

Hemiketal

Explanation:

This is a hemiketal. Hemiketals are formed from the reaction of a ketone with an alcohol. The alcohol attacks the carbonyl carbon, reducing the double bond and adding a hydroxyl group.

Example Question #3 : Identifying Carbonyl Compounds

Identify the given organic functional group.

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Possible Answers:

Acid anhydride

Hemiacetal

Hemiketal

Ketal

Acetal

Correct answer:

Ketal

Explanation:

Ketals have two -OR groups bound to a central carbon. The R groups attached to the oxygens are not necessarily the same. Ketals result from the reaction of a ketone with two equivalents of alcohol.

Example Question #1 : Identifying Carbonyl Compounds

Identify the given organic functional group.

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Possible Answers:

Acetal

Acid anhydride

Carboxylic acid

Ester

Hemiacetal

Correct answer:

Acid anhydride

Explanation:

Acid anhydrides are relatively reactive, since they have a fairly good leaving group (the conjugate base of a carboxylic acid) [COO-]. They are formed by reacting two carboxylic acids via dehydration synthesis.

Example Question #4 : Identifying Carbonyl Compounds

Identify the given organic functional group.

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Possible Answers:

Amide

Ester

Amine

Imine

Ether

Correct answer:

Amide

Explanation:

This is an amide. It is very unreactive since its leaving group is the conjugate base of an amine [HNR-]. 

Example Question #2 : Identifying Carbonyl Compounds

Identify the given organic functional group.

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Possible Answers:

Ketone

Carboxylic acid

Aldehyde

Ester

Ether

Correct answer:

Ester

Explanation:

Esters are relatively unreactive since the leaving group is an alkoxide ion (OR-), which is the conjugate base of an alcohol (a relatively weak acid). 

Example Question #4 : Identifying Carbonyl Compounds

Sigma and pie bonds

How many sigma and pi bonds, respectively, are there in the given molecule?

Possible Answers:

\(\displaystyle 8\) pi bonds, \(\displaystyle 1\) sigma bond

\(\displaystyle 8\) sigma bonds, \(\displaystyle 1\) pi bond

\(\displaystyle 9\) pi bonds, \(\displaystyle 1\) sigma bond

\(\displaystyle 9\) sigma bonds, \(\displaystyle 1\) pi bond

Correct answer:

\(\displaystyle 9\) sigma bonds, \(\displaystyle 1\) pi bond

Explanation:

To answer this question, it's important to recall what sigma bonds and pi bonds are. Sigma bonds are the result of overlapping s orbitals, and are contained in all bonds. Pi bonds, on the other hand, are the result of p orbitals overlapping.

Double bonds between atoms consist of one sigma bond (from overlapping s orbitals) and one pi bond (from overlapping p orbitals). Triple bonds, though not shown in this molecule, consist of one sigma bond and two pi bonds.

In the molecule shown in this question, we can recognize the following bonds:

1 carbon-oxygen double bond, which is equal to one sigma bond and one pi bond

2 carbon-carbon single bonds, which equates to two sigma bonds

6 carbon-hydrogen single bonds, which equals six sigma bonds

Adding these up, we obtain a total of nine sigma bonds and one pi bond.

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