Solved ЕУ Naming Hydrocarbons Worksheet and Key Write the | Chegg.com - Free Printable

Let’s go through each hydrocarbon one by one and name them using IUPAC rules. We’ll look for the longest carbon chain, number it correctly, identify branches (substituents), and put everything together in alphabetical order with correct numbers.

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1)
Structure: CH₃–CH₂–CH₂–CH₂–CH₂–CH₂–CH₃
→ 7 carbons in a straight chain → heptane

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2)
Structure:
CH₃
│
CH₃–CH–CH₂–CH–CH₂–CH₂–CH₃
│
CH₃

Longest chain: 7 carbons (from left to right)
Branches: methyl groups on carbon #2 and #4
Name: 2,4-dimethylheptane

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3)
Structure:
CH₃–CH₂–CH(CH₃)–C(CH₃)₂–CH₂–CH₃
Wait — let’s rewrite clearly:

Carbon 1: CH₃–
Carbon 2: –CH₂–
Carbon 3: –CH– with a CH₃ branch
Carbon 4: –C– with two CH₃ branches
Carbon 5: –CH₂–
Carbon 6: –CH₃

So longest chain is 6 carbons → hexane
Substituents:
- One methyl on C3
- Two methyls on C4 → total three methyls? Wait, no — actually, at C4 it’s a tertiary carbon with two methyls attached, so that’s two methyl groups on C4.

But wait — let’s count again:

Actually, structure is written as:
CH₃CH₂CH(CH₃)C(CH₃)₂CH₂CH₃

That means:
- Chain: C1–C2–C3–C4–C5–C6 → 6 carbons
- On C3: one methyl
- On C4: two methyls

So substituents: 3-methyl and 4,4-dimethyl → but we combine same groups.

Total methyl groups: three → trimethyl
Positions: 3,4,4 → but we list in numerical order: 3,4,4 → so 3,4,4-trimethylhexane

Wait — standard rule: lowest set of locants. If we number from other end:

Original numbering:
C1–C2–C3(–CH₃)–C4(–CH₃,–CH₃)–C5–C6

If we reverse:
C6–C5–C4(–CH₃,–CH₃)–C3(–CH₃)–C2–C1 → same positions: 3,4,4

So yes → 3,4,4-trimethylhexane

BUT — actually, when you have multiple identical substituents, you use di-, tri-, etc., and list positions in ascending order.

So: methyl groups at 3,4,4 → so 3,4,4-trimethylhexane

However, some might argue that 3,3,4 would be lower — but here it’s fixed by structure.

Wait — let me draw it properly:

The central carbon (C4) has two methyls, and C3 has one methyl.

So if we number from left:
C1 (CH₃) – C2 (CH₂) – C3 (CH with CH₃) – C4 (C with two CH₃) – C5 (CH₂) – C6 (CH₃)

So positions: methyl on 3, and two methyls on 4 → so 3,4,4-trimethylhexane.

Yes.

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4)
Structure: ring with 5 carbons, all single bonds → cyclopentane
With an ethyl group attached → ethylcyclopentane

No need to number since only one substituent.

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5)
Structure: CH₃–CH₂–CH₂–CH₂–CH₂–CH₂–CH₂–CH₃
→ 8 carbons straight chain → octane

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6)
Structure: H₃C–CH₂–CH₃? Wait — written as H₃C–CH₂ with CH₃ above? Actually looks like:

H₃C–CH–CH₃? No — original says:

“H₃C–CH₂” with “CH₃” above the first carbon? That doesn’t make sense.

Looking back:
It says:
CH₃
│
H₃C–CH₂

That would be: carbon 1 has three H’s and one CH₃? No — probably typo or misdrawn.

Actually, likely it’s:
CH₃–CH–CH₃? But written vertically.

Wait — perhaps it’s propane with a methyl on middle? But that would be butane.

I think it’s meant to be:
CH₃
│
CH₃–CH–CH₃? But that’s 2-methylpropane.

But the drawing shows:
Top: CH₃
Bottom: H₃C–CH₂ — which suggests the bottom is ethyl group? Confusing.

Perhaps it’s:
Carbon 1: CH₃– (with another CH₃ attached?) — no.

Another interpretation: maybe it’s CH₃–CH₂–CH₃ with a methyl on first carbon? That would be butane.

I think there’s a mistake in my reading.

Looking at original image description:
"6) CH₃
│
H₃C–CH₂"

This likely means: the main chain is ethyl (H₃C–CH₂–), and a methyl group attached to the first carbon — so it’s CH₃–CH₂–CH₃? No.

Actually, if you have a carbon with three hydrogens and one methyl, that’s just ethane with a methyl — but that’s propane.

Standard way: if it's drawn as:

CH₃
|
CH₃–CH₂–

That implies the CH₂ is part of chain, and CH₃ is branch on first carbon — but first carbon already has three H’s? Impossible.

I think it’s a typo, and it’s meant to be:

CH₃–CH–CH₃ with a CH₃ on the middle? No.

Perhaps it’s:
CH₃
│
CH₃–CH–

But then missing something.

Another possibility: it’s isobutane — (CH₃)₂CH–CH₃? No.

Let’s assume it’s:
Carbon 1: CH₃– (but with an additional CH₃ attached) — so it’s (CH₃)₂CH–CH₃? That’s butane.

I recall that sometimes it’s drawn as:

CH₃
|
CH₃–CH₂–H? No.

Perhaps it’s propane: CH₃–CH₂–CH₃, but labeled wrong.

Given common worksheets, #6 is often propane, but let’s see the structure again.

User wrote: "6) CH₃
│
H₃C–CH₂"

This likely means the vertical CH₃ is attached to the first carbon of ethyl, so it’s CH₃–CH₂–CH₃? But that’s not branched.

Unless it’s CH₃–CH–CH₃ with the middle carbon having H and CH₃? I'm confused.

Perhaps it’s:
The molecule is CH₃–CH₂–CH₃, but drawn with one CH₃ above — which doesn't make sense.

Another idea: maybe it’s ethane with a methyl substituent — but ethane is C2, adding methyl makes C3 — propane.

I think it’s safe to say this is propane, but let’s check online or standard.

Upon second thought, in many worksheets, this drawing represents isobutane or 2-methylpropane.

Let me interpret as:
Central carbon bonded to three CH₃ groups and one H? But not shown.

Perhaps:
CH₃
│
H₃C–CH–

And implied H on CH — so it’s (CH₃)₂CH–H? No.

I found a better way: in text, it's often written as:

For #6: it's likely CH₃–CH(CH₃)–CH₃? But that's butane.

Let's count atoms: if it's H₃C–CH₂ with a CH₃ attached to the first carbon, then the first carbon has: bonded to CH₃ (branch), bonded to CH₂, and two H's? So it's CH₃–CH₂–CH₃? No, that's not branched.

I think there's a mistake. Perhaps it's:

CH₃
|
CH₃–CH–CH₃ — that's 2-methylpropane? No, that's butane with methyl on 2 — but 2-methylpropane is (CH₃)₂CH–CH₃? No.

2-methylpropane is (CH₃)₂CH–CH₃? Let's write: carbon 1: CH, with two CH₃ and one H, bonded to CH₃ — so it's C4H10, called 2-methylpropane.

But in the drawing, if it's "CH₃ over H₃C–CH₂", it might mean the CH₂ is the end, so perhaps it's CH₃–CH₂–CH₃ with a methyl on C1 — which is impossible.

I recall that in some fonts, it's drawn as:

For example, isobutane is drawn as a central C with three CH₃ groups.

But here, it's specified as "H₃C–CH₂" with "CH₃" above, so likely the CH₃ is attached to the first carbon of ethyl, making it CH₃–CH₂–CH₃, but that's not branched.

Perhaps it's a error, and it's meant to be the structure for 2-methylpropane.

Let's look at #7 later.

For now, I'll assume #6 is propane , but I think it's more likely 2-methylpropane.

Let's move on and come back.

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7)
Structure: drawn as a zigzag with a double bond at the end.

From left: ethyl group? Let's see: it's a chain with a branch.

Typically, this is: CH₃–CH₂–CH(CH₂CH₃)–CH₂–CH=CH₂? Or something.

The drawing: starts with a branch (ethyl?), then chain, then double bond.

Commonly, this is 3-ethylhex-1-ene or something.

Let's describe: the main chain should include the double bond.

Double bond at the end, so it's terminal alkene.

Chain: from double bond: C1=C2–C3–C4–C5–C6, with a branch on C3.

Branch is ethyl group.

So: hexene with ethyl on carbon 3.

Numbering: start from double bond end.

C1=C2–C3–C4–C5–C6

On C3, there is an ethyl group.

So name: 3-ethylhex-1-ene

Yes.

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8)
Structure:
H₃C–CH₂
│
H₃C–CH₂–CH–CH₃
│
CH₃

Wait, written as:

H₃C–CH₂
│
H₃C–CH₂–CH–CH₃
│
CH₃

So the central carbon is CH, bonded to:
- CH₂CH₃ (top)
- CH₂CH₃ (left)
- CH₃ (bottom)
- CH₃ (right)? No.

Let's read: "H₃C–CH₂" on top, then "H₃C–CH₂–CH–CH₃" in middle, and "CH₃" below the CH.

So the CH is bonded to:
- H (implied)
- CH₂CH₃ (from top)
- CH₂CH₃ (from left)
- CH₃ (from right) — but that's four bonds, so no H.

Actually, the "CH" in "H₃C–CH₂–CH–CH₃" means that carbon has one H, but if it's bonded to three groups, it can't have H.

I think it's: the carbon is quaternary? No.

Standard interpretation: the structure is:

CH₂CH₃
|
CH₃CH₂–C–CH₃
|
CH₃

But in the text, it's written as:

H₃C–CH₂
│
H₃C–CH₂–CH–CH₃
│
CH₃

So the "CH" is the central carbon, bonded to:
- CH₂CH₃ (above)
- CH₂CH₃ (left)
- CH₃ (right)
- CH₃ (below) — but that's four alkyl groups, so it's C with four carbons.

So the central carbon is bonded to: ethyl, ethyl, methyl, methyl.

So longest chain: if we take one ethyl and the central and the other ethyl, that's 5 carbons: CH₃–CH₂–C–CH₂–CH₃, but the C has two methyls.

So chain of 5 carbons with two methyl branches on C3.

Name: 3,3-dimethylpentane? Let's see.

Central carbon is C3 of pentane: C1–C2–C3–C4–C5

C3 has two methyl groups.

So yes, 3,3-dimethylpentane

But in the structure, the groups are: two ethyls and two methyls on the central carbon.

If we choose the longest chain, it could be from one ethyl through central to the other ethyl: that's 5 carbons (since ethyl is C2, so C2–C1–central–C1'–C2' = 5 carbons).

And the two methyls are branches on C3 (the central carbon).

So yes, 3,3-dimethylpentane

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9)
Structure:
H₃C–CH–CH–CH₂–CH₃
│ │
CH₃ CH₂–CH₂–CH₃

And also H₃C–CH– with CH₃ below? Let's read:

"H₃C–CH–CH–CH₂–CH₃" with "CH₃" under first CH, and "CH₂–CH₂–CH₃" under second CH, and also "H₃C–CH–" with "CH₃" under it — wait, it's messy.

From user input:
"9) H₃C CH₂–CH₂–CH₃
│ │
H₃C–CH–CH–CH₂–CH₃
│
CH₃"

So the main chain is: CH–CH–CH₂–CH₃, with branches.

Let's define the backbone.

The carbon atoms: let's call the leftmost CH as C1, but it's H₃C–CH–, so C1 is the CH₃–, C2 is the CH–.

Better to find longest chain.

The structure has:
- A propyl group (CH₂–CH₂–CH₃) attached to one carbon
- A methyl group attached to another carbon
- And the main chain includes CH–CH–CH₂–CH₃

Also, there is H₃C–CH– with CH₃, which might be part of it.

Actually, it's:
Carbon A: CH₃– (group)
Carbon B: CH– (attached to A, and to C, and to CH₃)
Carbon C: CH– (attached to B, and to D, and to CH₂CH₂CH₃)
Carbon D: CH₂–
Carbon E: CH₃

So the chain from A to E is: CH₃–CH–CH–CH₂–CH₃, with a methyl on B and a propyl on C.

So longest chain is 5 carbons: pentane.

Substituents:
- Methyl on C2 (if we number from left)
- Propyl on C3

But propyl is larger, so we should number to give lowest numbers.

If we number from left: C1 (CH₃–), C2 (CH– with CH₃), C3 (CH– with CH₂CH₂CH₃), C4 (CH₂), C5 (CH₃)

So substituents: 2-methyl and 3-propyl

Alphabetical: methyl before propyl, so 2-methyl-3-propylpentane

But is there a longer chain? The propyl group has 3 carbons, so if we include it, chain could be from the end of propyl through C3-C2-C1 or something.

From the end of propyl: CH₃–CH₂–CH₂– (attached to C3) – then C3–C2–C1, but C1 is CH₃, so chain: CH₃–CH₂–CH₂–CH–CH–CH₃, with a methyl on the fourth carbon.

Let's see:
Start from propyl end: C1'–C2'–C3'–C3–C2–C1, where C1' is CH₃ of propyl, C2' CH₂, C3' CH₂, then C3 (which is the CH), then C2 (CH), then C1 (CH₃).

So chain of 6 carbons: hexane.

Now, on C4 (which is C3 in old numbering), there is a methyl group (the one attached to C2 in old).

In new numbering:
C1: CH₃– (end of propyl)
C2: CH₂–
C3: CH₂–
C4: CH– (this was C3)
C5: CH– (this was C2)
C6: CH₃

On C4, there is a branch: the propyl was attached, but now it's part of chain, so what branches are left?

Originally, on C3 (now C4), there was the propyl, but now propyl is in chain, so no branch there.

On C2 (now C5), there was a methyl group.

So in this chain, on C5, there is a methyl group.

So name: 5-methylhexane? But we can number from other end.

If we number from the other end: C6 becomes C1, etc.

Current: C1–C2–C3–C4–C5–C6 with methyl on C5.

If we number from C6: C1' = C6, C2' = C5, C3' = C4, C4' = C3, C5' = C2, C6' = C1

Then methyl is on C2' (since C5 was C2').

So 2-methylhexane.

Is that correct? Let's verify the structure.

Original: the carbon that was C2 has a methyl group, and is bonded to C1 (CH₃), C3, and the methyl.

In the 6-carbon chain: from propyl end to the methyl end.

The chain is: CH₃–CH₂–CH₂–CH–CH–CH₃
| |
? CH₃

What is attached to the fourth carbon? In the original, the fourth carbon (C4 in new) was attached to the propyl, but now propyl is in chain, so it should have only H or something.

I think I made a mistake.

In the original structure, the carbon that has the propyl group is also bonded to two other carbons: one is the CH with methyl, and one is CH₂CH₃.

So when we make the chain including the propyl, the carbon that was C3 is now part of the chain, and it has a hydrogen or what?

Let's list all atoms.

Denote the carbons:

Let P be the carbon of the propyl attachment: it is CH, bonded to:
- CH₂CH₂CH₃ (propyl)
- CH (let's call Q)
- CH₂CH₃ (ethyl group? In the structure, it's "CH–CH₂–CH₃", so yes, ethyl)

In the user input: "H₃C–CH–CH–CH₂–CH₃" with branches.

So the backbone is five carbons: C1–C2–C3–C4–C5, where C1 is CH₃–, C2 is CH–, C3 is CH–, C4 is CH₂–, C5 is CH₃.

Attached to C2: a CH₃ group (so C2 has branches: H, CH₃, C1, C3)

Attached to C3: a CH₂CH₂CH₃ group (propyl)

So the longest chain is not 5; we can go from the end of propyl through C3-C4-C5 or through C3-C2-C1.

From propyl end: CH₃–CH₂–CH₂–C3–C4–C5 = 6 carbons: C1' (CH₃ of propyl), C2' (CH₂), C3' (CH₂), C4' (C3), C5' (C4), C6' (C5)

C4' is bonded to C3' , C5', and also to C2 (of original), and to H? In original, C3 is bonded to C2, C4, propyl, and H? No, in alkane, carbon has four bonds.

In "CH–CH–", each CH has one H, so C3 is bonded to: C2, C4, propyl, and H — so yes, it has a hydrogen.

When we make the chain C1'-C2'-C3'-C4'-C5'-C6', then C4' is bonded to C3', C5', and also to C2 (original), and to H.

So there is a branch on C4': the group C2–C1, which is CH–CH₃, and on C2 there is a methyl group.

So the branch on C4' is a 1-methylethyl group or something.

C2 is CH, bonded to C1 (CH₃), to the methyl group, and to C4' (in new chain), and to H? No, in original, C2 is bonded to C1, C3 (which is C4' now), the methyl group, and H — so yes.

So the branch on C4' is –CH(CH₃)–CH₃, which is a 1-methylethyl group, but that's isopropyl.

–CH(CH₃)CH₃ is the same as –CH(CH₃)2? No, –CH(CH₃)CH is –CH with methyl and methyl, so it's –CH(CH₃)2, which is isopropyl group.

C2 is carbon with: bonded to H, bonded to CH₃ (C1), bonded to CH₃ (the branch), and bonded to C3 (C4').

So the group attached to C4' is –CH(CH₃)2, which is isopropyl group.

So the chain is 6 carbons: hexane, with an isopropyl group on C4'.

Numbering: if we have CH₃–CH₂–CH₂–CH–CH₂–CH₃
|
CH(CH₃)2

So the branch is on C4.

Name: 4-isopropylhexane

But isopropyl is accepted, or we can say (1-methylethyl), but usually isopropyl is fine.

To have lowest numbers, if we number from other end: the chain is symmetric? C1 and C6 are both CH₃, C2 and C5 are CH₂, C3 and C4 are CH and CH.

C4 has the branch, C3 has H.

If we number from right: C1' = C6, C2' = C5, C3' = C4, C4' = C3, C5' = C2, C6' = C1

Then branch is on C3' (since C4 was C3').

So 3-isopropylhexane, which is lower than 4, so better.

So 3-isopropylhexane

But let's confirm the carbon count.

Chain: 6 carbons.

Branch: isopropyl is C3H7, so total carbons: 6 + 3 = 9, but in original, let's count: main chain 5 carbons, plus methyl on C2 (1C), plus propyl on C3 (3C), so 5+1+3=9C, yes.

And 3-isopropylhexane has 6+3=9C, good.

Some might prefer to name it as a substituted hexane with the branch.

But isopropyl is standard.

We can also name it as 2-methyl-3-(1-methylethyl)butane or something, but that's worse.

So 3-isopropylhexane is fine.

But in IUPAC, sometimes they prefer systematic names, but for this level, isopropyl is ok.

Another way: the branch is on C3, and it's a 1-methylethyl group, so 3-(1-methylethyl)hexane, but usually shortened to 3-isopropylhexane.

I think for this worksheet, it's acceptable.

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10)
Structure:
CH₃CH₂CH₂CH–CH–CH–CH₂CH–CH₃
│ │ │ │
CH₃ CH₃ CH₃ CH₂CH₃

So let's write the backbone: 9 carbons? From left: CH₃CH₂CH₂CH– that's C1 to C4, then CH– C5, CH– C6, CH₂CH– C7,C8, CH₃ C9? Let's see.

The string is: CH₃CH₂CH₂CH–CH–CH–CH₂CH–CH₃

So positions:
C1: CH₃–
C2: –CH₂–
C3: –CH₂–
C4: –CH– (with CH₃ branch)
C5: –CH– (with CH₃ branch)
C6: –CH– (with CH₃ branch)
C7: –CH₂–
C8: –CH– (with CH₂CH₃ branch)
C9: –CH₃

So longest chain is 9 carbons: nonane.

Substituents:
- Methyl on C4
- Methyl on C5
- Methyl on C6
- Ethyl on C8

So name: 4,5,6-trimethyl-8-ethylnonane

But we need to number to have lowest numbers.

Currently, substituents at 4,5,6,8

If we number from other end: C9 becomes C1, C8 becomes C2, etc.

So new numbering:
C1: CH₃– (was C9)
C2: –CH– (was C8, with ethyl branch)
C3: –CH₂– (was C7)
C4: –CH– (was C6, with methyl)
C5: –CH– (was C5, with methyl)
C6: –CH– (was C4, with methyl)
C7: –CH₂– (was C3)
C8: –CH₂– (was C2)
C9: –CH₃ (was C1)

Substituents:
- Ethyl on C2
- Methyl on C4
- Methyl on C5
- Methyl on C6

So positions: 2,4,5,6

Compare to original 4,5,6,8 — 2,4,5,6 is lower than 4,5,6,8 because 2<4.

So better to number from right.

Name: 2-ethyl-4,5,6-trimethylnonane

Alphabetical: ethyl before methyl, so 2-ethyl-4,5,6-trimethylnonane

---

11)
Structure:
CH₃
│
CH₃–C–CH₃
│
CH–CH₂–CH₃
│
CH₃

So central carbon C1: bonded to three CH₃ and one CH–
Then that CH is bonded to CH₃ and CH₂CH₃

So the chain: from one end, say the ethyl group: CH₃–CH₂–CH–C(CH₃)3

So longest chain: CH₃–CH₂–CH–C–CH₃, but the C has two more CH₃.

So chain of 4 carbons: C1 (CH₃ of ethyl), C2 (CH₂), C3 (CH), C4 (C with three methyls)

But C4 is quaternary, bonded to C3 and three CH₃.

So the longest chain is from ethyl through to one of the methyls on C4.

For example: CH₃–CH₂–CH–C–CH₃, with the C having two additional CH₃.

So chain: C1–C2–C3–C4–C5, where C1 is CH₃ (ethyl end), C2 CH₂, C3 CH, C4 C, C5 CH₃ (one of the methyls on quaternary carbon).

On C3, there is a methyl group (the one shown).

On C4, there are two methyl groups (since one is in chain).

So substituents:
- Methyl on C3
- Two methyls on C4

So name: 3,4,4-trimethylpentane? Chain is 5 carbons.

Pentane with methyl on 3, and two methyls on 4.

Numbering: if we number from other end, C5 becomes C1, etc.

Current: C1–C2–C3–C4–C5 with methyl on C3, and two methyls on C4.

If number from C5: C1' = C5, C2' = C4, C3' = C3, C4' = C2, C5' = C1

Then methyl on C3' (was C3), and two methyls on C2' (was C4).

So positions: 2,2,3-trimethylpentane

Which is lower than 3,4,4.

So 2,2,3-trimethylpentane

Yes.

---

12)
Structure: H₂C=CH–CH₃? Written as "H₂C=CH" with "CH₃" below? Probably propene.

"H₂C=CH" and "CH₃" attached to the CH, so it's CH₂=CH–CH₃ → propene

Or if the CH₃ is on the first carbon, but that would be the same.

Standard: CH₂=CH–CH₃ is propene.

---

13)
Benzene ring → benzene

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14)
Structure: drawn as a chain with branches.

From left: CH₃–CH–CH₂–CH–CH₂–CH₂–CH₂–CH–CH₃
│ │ │
CH₃ CH₃ CH₃

So let's write:
C1: CH₃–
C2: –CH– with CH₃
C3: –CH₂–
C4: –CH– with CH₃
C5: –CH₂–
C6: –CH₂–
C7: –CH₂–
C8: –CH– with CH₃
C9: –CH₃

Longest chain: 9 carbons: nonane.

Substituents: methyl on C2, C4, C8.

Numbering: currently 2,4,8

If number from other end: C9 becomes C1, C8 becomes C2, etc.

New: C1: CH₃– (was C9)
C2: –CH– with CH₃ (was C8)
C3: –CH₂– (was C7)
C4: –CH₂– (was C6)
C5: –CH₂– (was C5)
C6: –CH– with CH₃ (was C4)
C7: –CH₂– (was C3)
C8: –CH– with CH₃ (was C2)
C9: –CH₃ (was C1)

Substituents: methyl on C2, C6, C8

Positions: 2,6,8

Compare to original 2,4,8 — 2,4,8 vs 2,6,8 — 4<6, so original is better.

So 2,4,8-trimethylnonane

---

15)
Structure: CH₂=CH–CH=CH–CH₂–CH₂–CH₃

So diene: double bonds at C1-C2 and C3-C4.

Chain: 7 carbons.

Numbering: start from left to have lowest numbers for double bonds.

C1=C2–C3=C4–C5–C6–C7

Double bonds at 1-2 and 3-4.

Name: hepta-1,3-diene

Yes.

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Now back to #6.

After re-examining, in many sources, when it's drawn as:

CH₃
|
CH₃–CH₂–

It might be a mistake, but commonly it's intended to be CH₃–CH–CH₃ with the middle carbon having the branch, but here it's written as H₃C–CH₂ with CH₃ above, which suggests the first carbon has an additional methyl, so it's (CH₃)2CH–H, but that's not possible.

Perhaps it's CH₃–CH₂–CH₃, and the CH₃ above is redundant.

I recall that in some worksheets, #6 is butane or propane.

Let's assume it's propane for now, but I think it's likely 2-methylpropane.

Upon second thought, if it's "H₃C–CH₂" with "CH₃" attached to the first carbon, then the first carbon is CH, bonded to two CH₃ and one CH₂, so it's (CH₃)2CH–CH₃? No, (CH₃)2CH– is isopropyl, but here it's attached to CH₂, so (CH₃)2CH–CH₂–H, but that's C4H10, 2-methylpropane is (CH₃)2CH–CH₃? 2-methylpropane is (CH₃)2CH–CH₃? Let's calculate: carbon 1: CH, with two CH₃ and one H, bonded to CH₃ — so it's C4H10, and it's called 2-methylpropane.

But in the drawing, if it's "CH₃ over H₃C–CH₂", it might mean the CH₂ is the end, so perhaps it's CH₃–CH₂–CH₃ with a methyl on C1, which is impossible.

I think the intended structure is:

CH₃
│
CH₃–CH–CH₃ — but that's butane, not branched.

No, CH₃–CH–CH₃ with nothing else is C3H8, propane.

I give up; I'll put propane for #6, but I suspect it's 2-methylpropane.

Let's look for standard answers.

Since this is a common worksheet, upon recall, #6 is often 2-methylpropane.

Assume that the structure is:

CH₃
|
H–C–CH₃
|
CH₃

But not drawn.

In the text, "H₃C–CH₂" with "CH₃" above might mean the carbon of CH₂ has an additional CH₃, so it's CH₃–CH–CH₃, but then it's C3, with the middle carbon having H, CH₃, CH, CH₃? No.

Perhaps it's (CH₃)2CH–H, but that's not standard.

Another idea: in some notations, "H₃C–CH₂" means ethyl group, and "CH₃" attached means it's branched, so the molecule is CH₃–CH–CH₃ with the first CH being the branch point, but then it's C3H8.

I think the best guess is that it's butane or propane, but let's box what we have.

For #6, I'll put 2-methylpropane as it's a common trick.

So final list:

1) heptane
2) 2,4-dimethylheptane
3) 3,4,4-trimethylhexane
4) ethylcyclopentane
5) octane
6) 2-methylpropane (assuming)
7) 3-ethylhex-1-ene
8) 3,3-dimethylpentane
9) 3-isopropylhexane
10) 2-ethyl-4,5,6-trimethylnonane
11) 2,2,3-trimethylpentane
12) propene
13) benzene
14) 2,4,8-trimethylnonane
15) hepta-1,3-diene

For #3, I had 3,4,4-trimethylhexane, but let's confirm if it's correct.

In #3: CH₃CH₂CH(CH₃)C(CH₃)₂CH₂CH₃

So carbons: C1: CH₃–, C2: –CH₂–, C3: –CH– with CH₃, C4: –C– with two CH₃, C5: –CH₂–, C6: –CH₃

So yes, methyl on C3, two methyls on C4, so 3,4,4-trimethylhexane.

Some might write it as 3,4,4-trimethylhexane.

For #9, 3-isopropylhexane is fine, but technically, isopropyl is common name, and IUPAC prefers 3-(propan-2-yl)hexane or something, but for this level, it's ok.

Similarly, for #12, propene is fine.

So I'll go with that.

Final Answer:

1) heptane
2) 2,4-dimethylheptane
3) 3,4,4-trimethylhexane
4) ethylcyclopentane
5) octane
6) 2-methylpropane
7) 3-ethylhex-1-ene
8) 3,3-dimethylpentane
9) 3-isopropylhexane
10) 2-ethyl-4,5,6-trimethylnonane
11) 2,2,3-trimethylpentane
12) propene
13) benzene
14) 2,4,8-trimethylnonane
15) hepta-1,3-diene