Organic Chemistry Functional Group Worksheet showing structural formulas and identification of functional groups.

Let’s go through each compound one by one. We’ll identify the functional group in each — that’s the special part of the molecule that gives it its chemical behavior. I’ll name the functional group and tell you which atoms to circle (in your mind or on paper).

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Row 1, Left:
Structure: CH₃–CH₂–CHO
This has a carbon double-bonded to oxygen AND bonded to hydrogen at the end → Aldehyde
→ Circle: C=O and the H attached to that same carbon.

Row 1, Right:
Structure: CH₃–CH₂–CH(OH)–CH₃
Has an –OH group attached to a carbon → Alcohol
→ Circle: the O and H in the OH group.

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Row 2, Left:
Structure: CH₃–CH₂–COOH
Has a carbon double-bonded to O and also bonded to OH → Carboxylic Acid
→ Circle: the C=O and the O–H together.

Row 2, Right:
Structure: CH₃–CH₂–CH₂–CH₂–CH₃
Only single bonds between carbons and hydrogens → Alkane (no real “functional group” but we say alkane for saturated hydrocarbon)
→ No specific functional group to circle — just note it’s all single bonds.

Wait — actually, alkanes don’t have a functional group per se. But since the worksheet says “name the functional group”, and this is just carbon chain with H’s, we can say “none” or “alkane”. But let’s check again — maybe they expect “alkyl” or something? Actually, no — standard answer: No functional group or sometimes called “alkane backbone”.

But looking at other structures, perhaps they want us to recognize if there’s any reactive group. This one doesn’t have any. So we’ll say: None (alkane)

Actually, wait — let me recheck the structure:

It’s written as:
H H H H H
| | | | |
H-C-C-C-C-C-H
| | | |
H H H H

Yes — pentane. Only C-C and C-H bonds → Alkane, no functional group.

But some teachers might accept “alkane” as the category. Let’s keep going.

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Row 3, Left:
Structure: CH₃–CH=CH–CH₃
Double bond between two carbons → Alkene
→ Circle the C=C double bond.

Row 3, Right:
Structure: CH₃–CH₂–CH₂–CHO
Again, ends with C=O and H → Aldehyde
→ Circle the terminal C=O and the H attached to that carbon.

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Row 4, Left:
Structure: CH₃–COOH
Same as row 2 left — carboxylic acid → Carboxylic Acid
→ Circle C=O and O–H.

Row 4, Right:
Structure: CH₃–CH₂–CH₂–C≡CH
Triple bond at the end → Alkyne
→ Circle the C≡C triple bond.

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Row 5, Left:
Structure: CH₃–CH₂–CH₂–CO–CH₃
Carbon double-bonded to O, and that carbon is between two other carbons → Ketone
→ Circle the C=O group (the carbon is bonded to two other carbons).

Row 5, Right:
Structure: CH₃–CH₂–CH₂–CH₂–CHO
Ends with C=O and H → Aldehyde
→ Circle the terminal C=O and H.

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Row 6, Left:
Structure: CH₃–CH₂–CH(OH)–CH₂–CH₃
Has –OH group → Alcohol
→ Circle the O and H in OH.

Row 6, Right:
Structure: CH₃–CO–CH₃
Middle carbon double-bonded to O, bonded to two methyl groups → Ketone
→ Circle the C=O.

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Row 7, Left:
Structure: CH₃–CH₂–CH₂–C≡C–CH₃
Triple bond in the middle → Alkyne
→ Circle the C≡C.

Row 7, Right:
Structure: CH₂=CH–CH₃
Double bond at start → Alkene
→ Circle the C=C.

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Row 8, Left:
Structure: CH₃–OH
Just one carbon with OH → Alcohol (specifically methanol)
→ Circle the O–H.

Row 8, Right:
Structure: CH₃–CH₂–CH₂–COOH
Ends with COOH → Carboxylic Acid
→ Circle the C=O and O–H.

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Now let’s compile the answers clearly for each box.

We’ll list them row by row, left then right.

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Final Answer:

Row 1:
Left: Aldehyde — circle the C=O and the H attached to that carbon.
Right: Alcohol — circle the OH group.

Row 2:
Left: Carboxylic Acid — circle the COOH group (C=O and O–H).
Right: Alkane — no functional group (or write “none”).

Row 3:
Left: Alkene — circle the C=C double bond.
Right: Aldehyde — circle the terminal C=O and H.

Row 4:
Left: Carboxylic Acid — circle the COOH group.
Right: Alkyne — circle the C≡C triple bond.

Row 5:
Left: Ketone — circle the C=O (carbon bonded to two other carbons).
Right: Aldehyde — circle the terminal C=O and H.

Row 6:
Left: Alcohol — circle the OH group.
Right: Ketone — circle the C=O.

Row 7:
Left: Alkyne — circle the C≡C.
Right: Alkene — circle the C=C.

Row 8:
Left: Alcohol — circle the OH.
Right: Carboxylic Acid — circle the COOH group.

Note: For Row 2 Right (pentane), since it's just an alkane with no functional group, you can write "None" or "Alkane" depending on what your teacher expects. Most worksheets consider alkanes to have no functional group.

✔ All done! Make sure to circle the correct atoms in each structure as described.