---
title: "2-Methylpropane | Organic Chemistry"
description: "2-methylpropane is a branched C4H10 alkane, also called isobutane, whose shape affects boiling point, naming, and isomer comparisons in Organic Chemistry."
canonical: "https://fiveable.me/organic-chem/key-terms/2-methylpropane"
type: "key-term"
subject: "Organic Chemistry"
unit: "Unit 3"
---

# 2-Methylpropane | Organic Chemistry

## Definition

2-methylpropane is the branched alkane C4H10, also called isobutane. In Organic Chemistry, it is the branched isomer of butane that you use to compare structure, naming, and physical properties.

## What It Is

2-methylpropane is a branched alkane in Organic Chemistry, with the formula C4H10. Its carbon skeleton has three carbons in the longest chain and one methyl group attached to carbon 2, so the structure is compact instead of straight.

You may also see it called isobutane. That older common name points to the same molecule, but the IUPAC name tells you exactly how the atoms are arranged. When you read 2-methylpropane, the name itself is a clue that propane is the parent chain and a methyl substituent sits on the second carbon.

This molecule matters because it is one of the simplest examples of chain isomerism. 2-methylpropane and n-butane both have the same molecular formula, C4H10, but different connectivity. Same formula, different structure means different properties, which is a big theme throughout organic chemistry.

The branch changes the shape of the molecule. A straight-chain molecule like n-butane can line up more easily with neighboring molecules, while the branched shape of 2-methylpropane is more compact. That usually lowers the strength of intermolecular attractions enough to affect physical properties such as boiling point. This is why branched alkanes often boil at lower temperatures than their straight-chain isomers.

The branching also matters for naming practice. If you can identify the longest chain, number it correctly, and place the substituent on the right carbon, you can move from a drawing to the correct IUPAC name. 2-methylpropane is a good early example because the name is short, but it still forces you to think about parent chain selection, substituents, and isomer recognition all at once.

It is still an alkane, so it only has single bonds and is fairly unreactive compared with compounds that contain double bonds, triple bonds, or functional groups. In many problems, its main job is to show how structure affects properties rather than to act as a reactive starting material.

## Why It Matters

2-methylpropane shows up any time Organic Chemistry asks you to connect structure with property. If you can explain why this branched isomer behaves differently from n-butane, you are already using one of the main ideas in the chapter on alkanes and alkane isomers.

It also gives you a clean model for IUPAC naming. The name 2-methylpropane is a worked example of finding the parent chain, identifying a substituent, and numbering the chain so the substituent gets the lowest possible number. That same naming logic carries into larger molecules, where the mistakes are easier to make.

You also use it as a comparison point for physical properties. Because 2-methylpropane is more compact than n-butane, its intermolecular forces differ in measurable ways. That kind of comparison is common in lab questions, multiple-choice items, and short-answer prompts that ask you to explain trends instead of just listing them.

Finally, it helps you separate formula from structure. C4H10 does not tell you everything. Organic Chemistry keeps returning to that idea, and 2-methylpropane is one of the first molecules that makes the point clearly.

## Connections

### Alkanes

2-methylpropane belongs to the alkane family, so it fits the pattern of saturated hydrocarbons with only single bonds. That means it is a simple baseline molecule before you add functional groups or unsaturation. When a question asks you to identify whether a molecule is an alkane, 2-methylpropane is a straightforward yes, because it contains only carbon and hydrogen bonded by single bonds.

### Isomers

2-methylpropane is one of the classic examples of isomerism because it shares the formula C4H10 with n-butane but has a different connectivity. This is the kind of comparison that shows why formulas alone are not enough in Organic Chemistry. If two compounds are isomers, they can have different names, shapes, and physical properties even when the atom count is identical.

### [Branched-chain Alkanes](/organic-chem/key-terms/branched-chain-alkanes)

This molecule is branched rather than straight-chain, so it is a direct example of how branching changes molecular shape. Branched alkanes tend to be more compact, which affects boiling point and packing. When you compare several C4 or C5 alkanes, 2-methylpropane is one of the easiest ways to see branching in action.

### [IUPAC Nomenclature](/organic-chem/key-terms/iupac-nomenclature)

The name 2-methylpropane is a naming exercise in miniature. You need to spot the longest chain, name it as propane, then identify the methyl group on carbon 2. If you can name this molecule correctly, you are practicing the same steps you will use for bigger branched hydrocarbons.

## On the AP Exam

A quiz question might give you a skeletal or condensed structure and ask you to name it, or give you the name 2-methylpropane and ask you to draw the structure. You may also need to compare it with n-butane and explain why the branched isomer has a different boiling point. In problem sets, this term usually shows up in naming practice, isomer identification, or property trend questions. If your class uses model kits or structure drawings, you should be able to point out the longest chain and the methyl branch without guessing.

## 2-methylpropane vs n-butane

These two compounds both have the formula C4H10, so they are easy to mix up. The difference is connectivity: n-butane is a straight chain, while 2-methylpropane is branched. That structural difference changes the molecule's shape and physical properties, especially boiling point.

## Key Takeaways

- 2-methylpropane is a branched alkane with the formula C4H10, and its common name is isobutane.
- It is an isomer of n-butane, so the two molecules have the same formula but different connectivity.
- The IUPAC name tells you the structure: propane is the parent chain, and a methyl group is attached to carbon 2.
- Its branched shape makes it more compact than n-butane, which affects physical properties like boiling point.
- You use this molecule as a basic example for naming, isomer comparisons, and structure-property relationships in Organic Chemistry.

## FAQs

### What is 2-methylpropane in Organic Chemistry?

2-methylpropane is a branched alkane with the molecular formula C4H10. It is the same compound as isobutane, and it is the branched isomer of n-butane. In Organic Chemistry, it is often used to show how carbon skeletons can differ even when the formula stays the same.

### Is 2-methylpropane the same as isobutane?

Yes. Isobutane is the common name, and 2-methylpropane is the IUPAC name for the same molecule. The IUPAC name is more precise because it shows the branching pattern directly.

### How is 2-methylpropane different from n-butane?

They have the same formula, C4H10, but different structures. n-Butane is a straight chain, while 2-methylpropane is branched. That difference changes the molecule's shape and usually lowers the boiling point of the branched isomer.

### Why does branching matter for 2-methylpropane?

Branching makes the molecule more compact, which changes how molecules pack together and how strongly they attract each other. In this chapter, that is why branched alkanes are compared with straight-chain alkanes when you talk about physical properties and isomer trends.

## Related Study Guides

- [3.2 Alkanes and Alkane Isomers](/organic-chem/unit-3/alkanes-alkane-isomers/study-guide/8sOigMEvTudbWHpZ)

## About This Document

Canonical Fiveable pages are available as Markdown at the same path plus `.md`.

- [llms.txt](https://fiveable.me/llms.txt): index of Fiveable's sections and URL patterns
- [llms-full.txt](https://fiveable.me/llms-full.txt): complete subject and unit listing
- [MCP server](https://fiveable.me/mcp): call Fiveable as tools instead of fetching pages (`https://fiveable.me/api/mcp`)
- [MCP server for AP teachers](https://fiveable.me/mcp/teachers): a teacher's classes, assignments and AP-rubric grading (`https://fiveable.me/api/mcp/teacher`)

## Structured Data

```json
{"@context":"https://schema.org","@graph":[{"@type":"LearningResource","@id":"https://fiveable.me/organic-chem/key-terms/2-methylpropane#resource","name":"2-Methylpropane | Organic Chemistry","url":"https://fiveable.me/organic-chem/key-terms/2-methylpropane","learningResourceType":"Concept explainer","educationalLevel":"AP® / High School","about":{"@id":"https://fiveable.me/organic-chem/key-terms/2-methylpropane#term"},"audience":{"@type":"EducationalAudience","educationalRole":"student"},"dateModified":"2026-07-03T02:23:39.422Z","isPartOf":{"@type":"Collection","name":"Organic Chemistry Key Terms","url":"https://fiveable.me/organic-chem/key-terms"},"author":{"@type":"Organization","@id":"https://fiveable.me/editorial#content-team","name":"Fiveable Content Team","url":"https://fiveable.me/editorial","parentOrganization":{"@id":"https://fiveable.me/#organization"},"member":[{"@type":"Person","name":"Amanda DoAmaral","sameAs":["https://www.linkedin.com/in/adoamaral"]},{"@type":"Person","name":"Becky Bahr","sameAs":["https://www.linkedin.com/in/becky-bahr-b52743132"]}]},"publisher":{"@type":"Organization","name":"Fiveable","url":"https://fiveable.me"}},{"@type":"DefinedTerm","@id":"https://fiveable.me/organic-chem/key-terms/2-methylpropane#term","name":"2-methylpropane","description":"2-methylpropane is the branched alkane C4H10, also called isobutane. In Organic Chemistry, it is the branched isomer of butane that you use to compare structure, naming, and physical properties.","url":"https://fiveable.me/organic-chem/key-terms/2-methylpropane","inDefinedTermSet":{"@type":"DefinedTermSet","name":"Organic Chemistry Key Terms","url":"https://fiveable.me/organic-chem/key-terms"}},{"@type":"FAQPage","mainEntity":[{"@type":"Question","name":"What is 2-methylpropane in Organic Chemistry?","acceptedAnswer":{"@type":"Answer","text":"2-methylpropane is a branched alkane with the molecular formula C4H10. It is the same compound as isobutane, and it is the branched isomer of n-butane. In Organic Chemistry, it is often used to show how carbon skeletons can differ even when the formula stays the same."}},{"@type":"Question","name":"Is 2-methylpropane the same as isobutane?","acceptedAnswer":{"@type":"Answer","text":"Yes. Isobutane is the common name, and 2-methylpropane is the IUPAC name for the same molecule. The IUPAC name is more precise because it shows the branching pattern directly."}},{"@type":"Question","name":"How is 2-methylpropane different from n-butane?","acceptedAnswer":{"@type":"Answer","text":"They have the same formula, C4H10, but different structures. n-Butane is a straight chain, while 2-methylpropane is branched. That difference changes the molecule's shape and usually lowers the boiling point of the branched isomer."}},{"@type":"Question","name":"Why does branching matter for 2-methylpropane?","acceptedAnswer":{"@type":"Answer","text":"Branching makes the molecule more compact, which changes how molecules pack together and how strongly they attract each other. In this chapter, that is why branched alkanes are compared with straight-chain alkanes when you talk about physical properties and isomer trends."}}]},{"@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Organic Chemistry","item":"https://fiveable.me/organic-chem"},{"@type":"ListItem","position":2,"name":"Key Terms","item":"https://fiveable.me/organic-chem/key-terms"},{"@type":"ListItem","position":3,"name":"Unit 3","item":"https://fiveable.me/organic-chem/unit-3"},{"@type":"ListItem","position":4,"name":"2-methylpropane"}]}]}
```