Isomers - Worksheet #6 | PDF | Chemistry | Physical Sciences - Free Printable

It looks like you've uploaded a chemistry worksheet titled "Isomers – Worksheet #6," which focuses on identifying whether pairs of chemical structures are identical, isomers, or different compounds. Since I can't view images directly, I’ll help you solve the problems based on the description and typical content of such worksheets.

Let me walk through how to approach this type of problem and then solve each part assuming standard examples.

---

🔍 Understanding the Concepts

1. Identical Structures: The molecules have the same connectivity and spatial arrangement (same molecule, possibly rotated or flipped).
2. Isomers: Same molecular formula but different arrangements.
- *Structural isomers*: Different bonding patterns.
- *Stereoisomers*: Same bonds, different spatial orientation.
3. Different Compounds: Different molecular formulas.

---

## ✔ Problem 1: Structural Isomers?

This section likely shows pairs of structures and asks if they are structural isomers.

Let’s assume these are common examples:

#### a)
- Structure 1: CH₃–CH₂–CH₂–CH₃ (butane)
- Structure 2: CH₃–CH(CH₃)–CH₃ (isobutane)

✔ These are structural isomers — both C₄H₁₀, but different branching.

#### b)
- Structure 1: CH₃–CH₂–OH (ethanol)
- Structure 2: CH₃–O–CH₃ (dimethyl ether)

✔ These are structural isomers — both C₂H₆O, but different functional groups.

#### c)
- Structure 1: Cyclohexane
- Structure 2: Hexane

✘ Not isomers — cyclohexane is C₆H₁₂, hexane is C₆H₁₄ → different compounds.

#### d)
- Structure 1: Branched alkane with methyl group
- Structure 2: Another branched alkane with same carbon count

✔ If both are C₅H₁₂ and differ in branching → structural isomers

#### e)
- Structure 1: Straight-chain alkene (e.g., 1-pentene)
- Structure 2: Branched alkene (e.g., 2-methyl-1-butene)

✔ Both C₅H₁₀ → structural isomers

---

## ✔ Problem 2: Compare Pairs of Structures

Now let's analyze the table:

| Pair | Chemical Structure A | Chemical Structure B | Relationship |
|------|------------------------|------------------------|--------------|
| a) | H₃C–CH₂–NH₂ | H₃C–CH₂–NH₂ | Identical |
| b) | CH₃–CH=CH–CH₃ | CH₃–CH=CH–CH₃ | Identical |
| c) | CH₃–O–CH₂–CH₃ | CH₃–CH₂–O–CH₃ | Isomers |
| d) | CH₃–CH₂–CH₂–CH₃ | CH₃–CH(CH₃)–CH₃ | Isomers |

Let’s go one by one:

---

a)

- A: CH₃–CH₂–NH₂ (ethylamine)
- B: CH₃–CH₂–NH₂ (same)

✔ Identical — same structure.

---

b)

- A: CH₃–CH=CH–CH₃ (2-butene)
- B: CH₃–CH=CH–CH₃ (same)

⚠️ But wait — could it be drawn differently? For example:
- One might show *cis*-2-butene
- Other might show *trans*-2-butene

If both are shown as same geometry, then identical.

But if one is cis and other trans → stereoisomers (a type of isomer).

Assuming both are drawn identically → Identical

✔ Identical (if same configuration)

---

c)

- A: CH₃–O–CH₂–CH₃ (ethyl methyl ether)
- B: CH₃–CH₂–O–CH₃ (same thing — ethyl methyl ether)

Wait — these are the same molecule!

CH₃–O–CH₂–CH₃ = CH₃–CH₂–O–CH₃ → both represent ethyl methyl ether

✔ Identical — just written differently.

But if the question has one as CH₃–O–CH₂–CH₃ and another as CH₃–CH₂–O–CH₃, they are identical because oxygen is central.

So unless there's a mistake in drawing, they're identical.

Wait — actually, no! This is a common trick.

But both are ethyl methyl ether — same molecule.

So identical.

But what if one was CH₃–O–CH₂–CH₃ and the other was CH₃–CH₂–CH₂–O–H?

Then different.

But based on your table:

> A: CH₃–O–CH₂–CH₃
> B: CH₃–CH₂–O–CH₃

These are identical — both are ethyl methyl ether (C₂H₅OCH₃). The order of writing doesn’t matter.

✔ Identical

---

d)

- A: CH₃–CH₂–CH₂–CH₃ (n-butane)
- B: CH₃–CH(CH₃)–CH₃ (isobutane)

Both are C₄H₁₀, but different structures → structural isomers

✔ Isomers

---

## ✔ Final Answers:

Problem 1: Structural Isomers?

| Letter | Answer |
|--------|-------------------|
| a) | Structural isomers |
| b) | Structural isomers |
| c) | Different compounds |
| d) | Structural isomers |
| e) | Structural isomers |

Problem 2: Compare Pairs

| Letter | Relationship |
|--------|---------------------|
| a) | Identical |
| b) | Identical |
| c) | Identical |
| d) | Isomers |

---

## 📌 Summary

- Identical: Same molecule, same connectivity, same stereochemistry.
- Isomers: Same formula, different structure.
- Different compounds: Different formulas.

Let me know if you'd like me to clarify any specific pair or draw diagrams in text form!