Organic Chemistry : Organic Functional Groups

Study concepts, example questions & explanations for Organic Chemistry

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Example Questions

Example Question #11 : Organic Functional Groups And Molecules

Octagon

Assuming that this molecule is planar, determine whether this molecule is aromatic, and name the number of  electrons ( molecular orbitals).

Possible Answers:

Aromatic, 8  electrons

Aromatic, 6  electrons

Non aromatic, 6  electrons

Not aromatic, 8  electrons

Correct answer:

Not aromatic, 8  electrons

Explanation:

There is no p orbital surrounding the Boron atom, so the ring does not have a fully conjugated pi system. In addition, there are 8  electrons, which does not follow Huckel's rule (an aromatic system contains 4n+2 electrons). The pi electrons include the lone pair (not shown, but implicit) on the nitrogen atom, which is why the answers with "6 electrons" are not correct.

Example Question #11 : Organic Functional Groups

1

Assuming that this molecule is planar, determine whether this molecule is aromatic, and name the number of  electrons (not  molecular orbitals). 

Possible Answers:

Aromatic, 6  electrons. 

Not aromatic, 8  electrons.

Aromatic, 8  electrons.

Not aromatic, 6  electrons. 

Correct answer:

Aromatic, 6  electrons. 

Explanation:

The lone pairs on the two nitrogen atoms reside in sp2 orbitals, meaning they do not participate in resonance. Within the ring, there are three  bonds, meaning there are six  electrons. Thus, the molecule is aromatic because it is planar and follows Huckel's rule. 

Example Question #11 : Organic Functional Groups

Identify the given organic functional group.

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Possible Answers:

Ketone

Aldehyde

Acid anhydride

Carboxylic acid

Ester

Correct answer:

Aldehyde

Explanation:

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

Example Question #2 : Identifying Carbonyl Compounds

Identify the given organic functional group.

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Possible Answers:

Ketone

Ester

Acetal

Aldehyde

Carboxylic acid

Correct answer:

Ketone

Explanation:

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

Example Question #1 : Identifying Carbonyl Compounds

Identify the given organic functional group.

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Possible Answers:

Acid halide

Ester

Acid anhydride

Amide

Carboxylic acid

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 #12 : Organic Functional Groups

Identify the given organic functional group.

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Possible Answers:

Ester

Carboxylic acid

Aldehyde

Ketone

Acid anhydride

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 #13 : Organic Functional Groups

Identify the given organic functional group.

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Possible Answers:

Ester

Hemiketal

Acid anhydride

Aldehyde

Acetal

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 #4 : Identifying Carbonyl Compounds

Identify the given organic functional group.

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Possible Answers:

Acid anhydride

Hemiketal

Acetal

Hemiacetal

Ketal

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 #2 : Identifying Carbonyl Compounds

Identify the given organic functional group.

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Possible Answers:

Carboxylic acid

Hemiacetal

Ester

Acid anhydride

Acetal

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 #6 : Identifying Carbonyl Compounds

Identify the given organic functional group.

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Possible Answers:

Amine

Ether

Ester

Amide

Imine

Correct answer:

Amide

Explanation:

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

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