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Ch. 4 - Alkanes and CycloalkanesWorksheetSee all chapters
All Chapters
Ch. 1 - A Review of General Chemistry
Ch. 2 - Molecular Representations
Ch. 3 - Acids and Bases
Ch. 4 - Alkanes and Cycloalkanes
Ch. 5 - Chirality
Ch. 6 - Thermodynamics and Kinetics
Ch. 7 - Substitution Reactions
Ch. 8 - Elimination Reactions
Ch. 9 - Alkenes and Alkynes
Ch. 10 - Addition Reactions
Ch. 11 - Radical Reactions
Ch. 12 - Alcohols, Ethers, Epoxides and Thiols
Ch. 13 - Alcohols and Carbonyl Compounds
Ch. 14 - Synthetic Techniques
Ch. 15 - Analytical Techniques: IR, NMR, Mass Spect
Ch. 16 - Conjugated Systems
Ch. 17 - Aromaticity
Ch. 18 - Reactions of Aromatics: EAS and Beyond
Ch. 19 - Aldehydes and Ketones: Nucleophilic Addition
Ch. 20 - Carboxylic Acid Derivatives: NAS
Ch. 21 - Enolate Chemistry: Reactions at the Alpha-Carbon
Ch. 22 - Condensation Chemistry
Ch. 23 - Amines
Ch. 24 - Carbohydrates
Ch. 25 - Phenols
Ch. 26 - Amino Acids, Peptides, and Proteins
Ch. 26 - Transition Metals
IUPAC Naming
Alkyl Groups
Naming Cycloalkanes
Naming Bicyclic Compounds
Naming Alkyl Halides
Naming Alkenes
Naming Alcohols
Naming Amines
Cis vs Trans
Conformational Isomers
Newman Projections
Drawing Newman Projections
Barrier To Rotation
Ring Strain
Axial vs Equatorial
Cis vs Trans Conformations
Equatorial Preference
Chair Flip
Calculating Energy Difference Between Chair Conformations
Additional Guides
t-Butyl, sec-Butyl, isobutyl, n-butyl
Johnny Betancourt

A butyl group is a four-carbon substituent that can be arranged in four different ways, and each form has its own name. 

P.S. Check out my 4-hour lesson on nomenclature if you’re not in a rush!

What are all the different four-carbon substituents? 

There are four different ways to arrange a four-carbon chain as a substituent, so let’s check them out! I’ve drawn them out on a cyclohexane as the parent molecule. There are more complex ways to name these alkyl groups, but we’ll be focusing on the common IUPAC names here. Remember that we use the suffix -yl here because we're referring to an R-group coming off of a molecule. If these were standalone alkanes, we'd use the suffix -ane (e.g. isobutane instead of isobutyl). 


This straight-chain butyl is called butyl, but you might also see it called n-butyl. “n” means straight-chain. It’s got only primary and secondary carbons.


This version, which looks a lot like isopropyl, is called isobutyl. It’s got primary, secondary, and tertiary carbons. 


This version, which looks like isopropyl with an extra carbon at the end, is called sec­-butyl. It’s got primary, sSec-butylecondary, and tertiary carbons. 


This version is called tert­-butyl. It’s got a quaternary carbon with three primary carbons coming off of it. Pro-tip: sometimes you'll see this abbreviated as t-bu. 

Hopefully this quick guide helps! Check out my videos on common substituents if you need a refresher!

Johnny Betancourt

Johnny got his start tutoring Organic in 2006 when he was a Teaching Assistant. He graduated in Chemistry from FIU and finished up his UF Doctor of Pharmacy last year. He now enjoys helping thousands of students crush mechanisms, while moonlighting as a clinical pharmacist on weekends.