Functional Group Flashcards: Names & Structures

Question 1

What does a functional group tell you about an organic molecule?

Accepted Answer

It identifies a characteristic bonding pattern that helps predict chemical behavior. Recognizing the group is a starting point; the rest of the molecule can still affect its reactions.

Question 2

In the condensed structure CH3–CH(CH3)–CH2–CH3, where does the parenthesized CH3 attach?

Accepted Answer

To the preceding CH carbon. Parentheses show a branch attached to the atom just before them.

Question 3

In an organic structural formula, why might two substituents be labeled R and R′?

Accepted Answer

They stand for groups whose full structures are omitted. The prime distinguishes the two positions; the groups may be the same or different. Check each formula’s definition of R, especially whether H is allowed.

Question 4

Functional group in CH3–CH=CH–CH3?

Accepted Answer

Alkene. The defining feature is a carbon–carbon double bond, C=C.

Question 5

Classify the oxygen-containing functional group in CH3–CH(OH)–CH2–CH3.

Accepted Answer

Alcohol. The –OH group is attached to a saturated carbon atom.

Question 6

Functional-group class of CH3–CH(Br)–CH2–CH3?

Accepted Answer

Haloalkane, also called an alkyl halide. Bromine is bonded directly to a saturated carbon atom.

Question 7

What bonding unit does C(=O) show in a condensed organic structure?

Accepted Answer

A carbonyl group: carbon double-bonded to oxygen. The atoms attached to that carbon determine the more specific functional-group class.

Question 8

Functional group in CH3–O–CH2–CH2–CH3?

Accepted Answer

Ether. One oxygen links two carbon groups through single bonds, and neither adjacent carbon is a carbonyl carbon.

Question 9

Functional group in CH3–C≡C–CH2–CH3?

Accepted Answer

Alkyne. Two carbon atoms are joined by a triple bond.

Question 10

What does Ph stand for in a condensed organic structure such as Ph–CH2–CH3?

Accepted Answer

A phenyl group, C6H5–: a benzene ring with one hydrogen replaced by a bond to the rest of the molecule.

Question 11

Functional group in CH3–CH2–NH–CH3?

Accepted Answer

Amine. Nitrogen has single bonds to two carbon groups and one hydrogen, making this a secondary amine.

Question 12

What bond defines an alkene functional group?

Accepted Answer

A carbon–carbon double bond, C=C, outside an aromatic ring. Carbon–oxygen double bonds belong to a different group family.

Question 13

What connectivity defines an alcohol group?

Accepted Answer

An –OH group bonded to a saturated carbon atom. That carbon has only single bonds; an OH directly on a benzene ring is classified separately.

Question 14

Classify the OH-containing group in Ph–OH, where Ph is a phenyl group (C6H5–).

Accepted Answer

Phenol. The oxygen of –OH is bonded directly to a carbon in the aromatic ring.

Question 15

Functional group in CH3–CH2–C≡N?

Accepted Answer

Nitrile. The carbon chain attaches to the carbon of a carbon–nitrogen triple bond.

Question 16

What connectivity defines a haloalkane (alkyl halide)?

Accepted Answer

A halogen bonded directly to a saturated carbon: C–X, where X is F, Cl, Br, or I. The carbon has only single bonds.

Question 17

A six-carbon ring is drawn with alternating single and double bonds to represent six delocalized π electrons. How is this ring classified?

Accepted Answer

An aromatic ring: the benzene-ring pattern. Its electrons are delocalized around the ring, so it is not treated as three separate alkene groups.

Question 18

What connectivity defines a simple ether group?

Accepted Answer

R–O–R′, with R and R′ attached through carbon and neither attached carbon being a carbonyl carbon. The oxygen has two single bonds and no O–H bond.

Question 19

Does CH3–CH2–CH2–CH3 contain a characteristic functional group in introductory organic classification?

Accepted Answer

No. It is an alkane with only C–C and C–H single bonds. Its saturated hydrocarbon framework is the comparison baseline.

Question 20

What are the three basic connectivity patterns for neutral amines?

Accepted Answer

R–NH2, R–NH–R′, and R–N(R′)–R″. Here each R is an alkyl or aryl group attached through carbon; the patterns have one, two, or three such groups on nitrogen.

Question 21

What bond defines an alkyne functional group?

Accepted Answer

A carbon–carbon triple bond, C≡C. Either end may connect to a carbon group or to hydrogen.

Question 22

What connectivity defines a phenol group?

Accepted Answer

An –OH group attached directly to a carbon of an arene ring. In the simplest example, phenol, the structure is C6H5–OH.

Question 23

What connectivity defines a nitrile group?

Accepted Answer

R–C≡N, with R attached through carbon. The triple bond joins carbon to nitrogen, and the rest of the molecule attaches on the carbon side.

Question 24

What ring structure is the standard introductory example of an aromatic group?

Accepted Answer

A benzene ring: six carbon atoms in a planar ring with six delocalized π electrons. It can be shown as a hexagon with a circle or with alternating single and double bonds.

Question 25

What single bond-order change distinguishes an alkene group from an alkyne group?

Accepted Answer

The carbon–carbon bond is double in an alkene and triple in an alkyne: C=C versus C≡C.

Question 26

Why is Ph–CH2–OH an alcohol, while Ph–OH is a phenol? (Ph = phenyl.)

Accepted Answer

In Ph–CH2–OH, OH attaches to the saturated CH2 carbon. In Ph–OH, OH attaches directly to the aromatic ring.

Question 27

Classify the nitrogen group in CH3–N(CH3)–CH2–CH3.

Accepted Answer

Tertiary amine. Nitrogen has three carbon substituents and no N–H bond; it is still an amine.

Question 28

Functional group in CH3–CH2–CH2–C(=O)H?

Accepted Answer

Aldehyde. The carbonyl carbon is bonded to a hydrogen and, here, to a carbon chain.

Question 29

Functional group in CH3–CH2–C(=O)–O–CH3?

Accepted Answer

Carboxylic ester. The carbonyl carbon is bonded to an oxygen that also bonds to a non-carbonyl carbon group.

Question 30

Functional group in CH3–CH2–C(=O)–CH2–CH3?

Accepted Answer

Ketone. The carbonyl carbon has a carbon atom attached on each side.

Question 31

Functional group in CH3–CH2–CH2–SH?

Accepted Answer

Thiol. Sulfur is bonded to a carbon group and to hydrogen.

Question 32

Functional group in CH3–CH2–C(=O)–NH2?

Accepted Answer

Amide, specifically a carboxamide. Nitrogen is bonded directly to the carbonyl carbon.

Question 33

Functional group in CH3–CH2–C(=O)–OH?

Accepted Answer

Carboxylic acid. An OH group and a double-bonded oxygen attach to the same carbon.

Question 34

Functional group in CH3–CH2–C(=O)–Cl?

Accepted Answer

Acid chloride, a carboxylic acid halide (acyl halide). Chlorine is bonded directly to the carbonyl carbon.

Question 35

Functional group in CH3–CH2–S–CH2–CH2–CH3?

Accepted Answer

Organic sulfide, also commonly called a thioether. One sulfur links two carbon groups through single bonds.

Question 36

Functional group in CH3–C(=O)–O–C(=O)–CH2–CH3?

Accepted Answer

Carboxylic acid anhydride. The central oxygen connects two carbonyl carbons; the carbon groups on the two sides can differ.

Question 37

What connectivity defines an aldehyde group, including formaldehyde?

Accepted Answer

R–C(=O)H, where R can be a carbon group or H. The carbonyl carbon has at least one attached hydrogen; formaldehyde is H–C(=O)–H.

Question 38

What local bonding feature separates a simple ether from a carboxylic ester?

Accepted Answer

An ester has a carbonyl carbon directly bonded to the linking oxygen: –C(=O)–O–C. A simple ether has C–O–C with neither adjacent carbon being a carbonyl carbon.

Question 39

Functional group in CH3–CH2–S–S–CH3?

Accepted Answer

Disulfide. Two sulfur atoms are bonded to each other, with a carbon group at each end.

Question 40

What connectivity defines a ketone group?

Accepted Answer

R–C(=O)–R′, with R and R′ both attached through carbon. Neither substituent on the carbonyl carbon is H.

Question 41

What attachment to nitrogen separates a carboxamide group from an amine group?

Accepted Answer

A carboxamide’s nitrogen is bonded directly to a carbonyl carbon. An amine’s nitrogen is bonded to alkyl or aryl groups instead of an acyl group.

Question 42

What connectivity defines a carboxylic acid group?

Accepted Answer

–C(=O)–OH, the carboxy group. The carbonyl carbon is directly bonded to the oxygen of OH.

Question 43

What connectivity defines a thiol group?

Accepted Answer

R–S–H, where R attaches through carbon. The S–H bond is the key recognition cue.

Question 44

Classify H–C(=O)–H by its carbonyl functional-group family.

Accepted Answer

Aldehyde. This is formaldehyde (methanal), whose carbonyl carbon has two attached hydrogens.

Question 45

What connectivity defines a carboxylic ester group?

Accepted Answer

R–C(=O)–O–R′. Here R is H or a carbon group, and R′ attaches through a non-carbonyl carbon. The linking oxygen has no O–H bond.

Question 46

What connectivity defines a carboxamide group, including N-substituted forms?

Accepted Answer

A carbonyl carbon bonded directly to nitrogen: –C(=O)–N. The nitrogen can carry H atoms or carbon substituents; an N–H bond is not required.

Question 47

What connectivity defines a carboxylic acid halide group?

Accepted Answer

–C(=O)–X, where X is a halogen attached directly to the carbonyl carbon. For an acid chloride, X is Cl.

Question 48

What connectivity defines a simple organic sulfide (thioether) group?

Accepted Answer

R–S–R′, with both groups attached through non-carbonyl carbon atoms. One sulfur bridges the two groups and has no S–H bond.

Question 49

What connectivity defines a carboxylic acid anhydride group?

Accepted Answer

–C(=O)–O–C(=O)–: one oxygen links two carbonyl carbons. The groups beyond the carbonyl carbons can be the same or different.

Question 50

Which attachments to the carbonyl carbon distinguish an aldehyde from a ketone?

Accepted Answer

An aldehyde has at least one attached H. A ketone has two attached carbon atoms and no H attached to the carbonyl carbon.

Question 51

Why is the OH in CH3–C(=O)–OH classified as part of a carboxylic acid rather than as an alcohol group?

Accepted Answer

Its oxygen attaches to a carbonyl carbon. An alcohol’s OH attaches to a saturated carbon; classify the whole –C(=O)–OH unit together.

Question 52

Which bond at sulfur distinguishes a thiol from a simple organic sulfide?

Accepted Answer

A thiol has S–H. A simple organic sulfide has sulfur bonded to two carbon groups and no S–H bond.

Question 53

What connectivity defines an organic disulfide group?

Accepted Answer

R–S–S–R′, with R and R′ attached through carbon. The central S–S bond distinguishes it from a single-sulfur bridge.

Question 54

Classify the nitrogen-containing group in CH3–C(=O)–N(CH3)–CH3.

Accepted Answer

Amide (carboxamide). Nitrogen is directly bonded to the carbonyl carbon, even though it has no N–H bond.

Question 55

How many carbonyl carbons bond directly to the linking oxygen in a carboxylic ester versus a carboxylic acid anhydride?

Accepted Answer

One in an ester; two in an anhydride. Follow both bonds from the linking oxygen to check.

Question 56

How does the carbon bonded to Cl differ in CH3–CH2–Cl and CH3–C(=O)–Cl?

Accepted Answer

It is a saturated carbon in CH3–CH2–Cl (haloalkane) and a carbonyl carbon in CH3–C(=O)–Cl (acid chloride).

Question 57

What changes in the bridge between carbon groups when a sulfide is compared with a disulfide?

Accepted Answer

A sulfide bridge has one sulfur, C–S–C; a disulfide bridge has two, C–S–S–C, including an S–S bond.

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Functional Group Flashcards: Names & Structures