--- title: "2-Butanol | Organic Chemistry" description: "2-Butanol is a secondary, chiral alcohol in Organic Chemistry, useful for naming, stereochemistry, IR, 13C NMR, and alcohol formation reactions." canonical: "https://fiveable.me/organic-chem/key-terms/2-butanol" type: "key-term" subject: "Organic Chemistry" unit: "Unit 13" --- # 2-Butanol | Organic Chemistry ## Definition 2-Butanol is a secondary alcohol with the formula CH3CH(OH)CH2CH3. In organic chemistry, it matters because it is chiral, spectroscopically distinct, and often shows up as a product of alcohol-forming reactions. ## What It Is 2-Butanol is a four-carbon secondary alcohol, written as CH3CH(OH)CH2CH3. The hydroxyl group is on carbon 2, so the carbon bearing the OH is attached to two other carbons. That placement is what makes it a secondary alcohol instead of a primary or tertiary one. The exact position of the OH group changes both naming and reactivity. Compare it with 1-butanol, where the OH is on an end carbon. In 2-butanol, the alcohol carbon sits in the middle of the chain, which changes how the molecule reacts in oxidation, substitution, and elimination reactions. It also gives the molecule a different shape in 3D. A big feature of 2-butanol in Organic Chemistry is chirality. Carbon 2 is attached to four different groups, so it is a stereocenter. That means 2-butanol exists as two enantiomers, which are mirror images that are not superimposable. If a reaction makes 2-butanol from an achiral starting material, the product can be a racemic mixture unless the mechanism or reagent controls stereochemistry. You will also see 2-butanol in spectroscopy problems. In IR, the O-H stretch shows up as a broad band around 3300 to 3600 cm^-1, which is the fast clue that an alcohol is present. In 13C NMR, each non-equivalent carbon gives its own signal, so 2-butanol produces six distinct carbon environments when you account for all chemically unique carbons in the structure and its symmetry-free arrangement. In reaction chapters, 2-butanol often appears as a product rather than just a molecule to memorize. For example, adding water to an achiral alkene like 2-butene gives 2-butanol. That makes it a nice example of how a flat alkene can become a molecule with a new stereocenter after addition across the double bond. ## Why It Matters 2-Butanol shows up in Organic Chemistry as a clean example of how structure controls behavior. One small change, putting the OH on carbon 2 instead of carbon 1, changes the alcohol class, the naming, the stereochemistry, and the kinds of reactions you expect. It is especially useful for connecting three big course ideas: alcohol naming, chirality, and spectroscopy. If you can identify 2-butanol quickly, you can also tell whether a product is chiral, predict the right IR peak, and read the carbon environments in a 13C NMR spectrum. It also shows up in synthesis and mechanism work. If a problem asks what alcohol forms after hydration of an alkene or after addition to a carbonyl, you may need to recognize 2-butanol as the product or as a close structural match. That makes it a practical checkpoint for reaction products, not just a vocabulary term. Because 2-butanol is a secondary alcohol, it also gives you a comparison point for 1-butanol and 2-propanol. Those comparisons help you sort alcohols by structure instead of trying to memorize each one separately. ## Connections ### Chirality 2-Butanol is chiral because carbon 2 is attached to four different groups. That makes it a good example of a stereocenter you can actually draw and check by hand. If you can spot the chiral carbon in 2-butanol, you can do the same kind of analysis on many other alcohols and reaction products. ### [1-butanol](/organic-chem/key-terms/1-butanol) 1-butanol is the closest naming comparison because it has the same carbon count but a different OH position. Moving the hydroxyl group from carbon 1 to carbon 2 changes the alcohol from primary to secondary, and it changes whether the molecule is chiral. That contrast is a common naming and structure question. ### [2-propanol](/organic-chem/key-terms/2-propanol) 2-propanol is another secondary alcohol, but it is not chiral because the carbon bearing the OH has two identical methyl groups. Comparing it with 2-butanol helps you see why a secondary alcohol is not always chiral. The difference is the rest of the carbon skeleton, not just the OH position. ### [1-butene](/organic-chem/key-terms/1-butene) 1-butene is a common starting alkene for making alcohols in addition reactions. When hydration adds H and OH across the double bond, the product can be 2-butanol depending on the mechanism and regiochemistry. This is a useful before-and-after pair for tracing how a pi bond turns into a saturated alcohol. ## On the AP Exam A quiz item might show a structure and ask you to name it, classify it, or identify whether it is chiral. You may also be asked to predict the product of alkene hydration or explain why a product is a racemic mixture. In spectroscopy questions, look for the broad O-H band in IR and the number of distinct carbon signals in 13C NMR. In a mechanism problem, 2-butanol can be the product you name after nucleophilic addition or hydration, so you need to connect the structure to the reaction pathway, not just the formula. ## 2-Butanol vs 1-butanol These two compounds have the same molecular formula, but the OH group is in a different place. 1-butanol is a primary alcohol with the OH on an end carbon, while 2-butanol is a secondary alcohol with the OH on carbon 2. That shift changes both naming and reactivity, and it also makes 2-butanol chiral while 1-butanol is not. ## Key Takeaways - 2-Butanol is a secondary alcohol with the structure CH3CH(OH)CH2CH3. - The OH group on carbon 2 makes the molecule chiral, so 2-butanol exists as enantiomers. - Its IR spectrum shows a broad O-H stretch around 3300 to 3600 cm^-1. - In 13C NMR, 2-butanol gives signals for its non-equivalent carbon environments. - It often appears as a product in hydration and alcohol-forming reaction problems. ## FAQs ### What is 2-butanol in Organic Chemistry? 2-Butanol is a four-carbon secondary alcohol with the OH group on the second carbon. Because that carbon is attached to two other carbons, the molecule is classified as secondary rather than primary. It is also chiral, which makes it a useful example in stereochemistry and spectroscopy. ### Is 2-butanol chiral? Yes. Carbon 2 is bonded to four different groups, so it is a stereocenter. That means 2-butanol has two enantiomers, which are mirror-image forms of the molecule. ### How do you identify 2-butanol on IR or NMR? In IR, look for the broad O-H stretch in the 3300 to 3600 cm^-1 region. In 13C NMR, count the distinct carbon environments in the structure, since each non-equivalent carbon gives its own signal. Those two tools are often enough to confirm that an alcohol like 2-butanol is present. ### How is 2-butanol different from 1-butanol? They have the same molecular formula, but the OH group sits on a different carbon. 1-butanol is primary because the OH is on carbon 1, while 2-butanol is secondary because the OH is on carbon 2. That difference changes the name, the classification, and the stereochemistry. ## Related Study Guides - [13.11 Characteristics of 13C NMR Spectroscopy](/organic-chem/unit-13/characteristics-13c-nmr-spectroscopy/study-guide/9CjlrP3nIXrf0Y7C) - [8.12 Reaction Stereochemistry: Addition of H2O to an Achiral Alkene](/organic-chem/unit-8/reaction-stereochemistry-addition-h2o-achiral-alkene/study-guide/JGOggLF78JS9ci5A) - [17.11 Spectroscopy of Alcohols and Phenols](/organic-chem/unit-17/spectroscopy-alcohols-phenols/study-guide/baa93fp90i6lBqq9) - [5.2 The Reason for Handedness in Molecules: Chirality](/organic-chem/unit-5/reason-handedness-molecules-chirality/study-guide/nAn5PnRoEBSQXE12) - [17.1 Naming Alcohols and Phenols](/organic-chem/unit-17/naming-alcohols-phenols/study-guide/o7NEMqk3w8HpPKRz) - [19.7 Nucleophilic Addition of Hydride and Grignard Reagents: Alcohol Formation](/organic-chem/unit-19/nucleophilic-addition-hydride-grignard-reagents-alcohol-formation/study-guide/z1vVGHUw2ftP8JJD) ## 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-butanol#resource","name":"2-Butanol | Organic Chemistry","url":"https://fiveable.me/organic-chem/key-terms/2-butanol","learningResourceType":"Concept explainer","educationalLevel":"AP® / High School","about":{"@id":"https://fiveable.me/organic-chem/key-terms/2-butanol#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-butanol#term","name":"2-Butanol","description":"2-Butanol is a secondary alcohol with the formula CH3CH(OH)CH2CH3. 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