Ch. 4 - Alkanes and CycloalkanesSee 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
Johnny Betancourt

An alkyl group is a saturated substituent consisting entirely of carbons and hydrogens. Its general formula is CnH2n+1.


P.S. Here is my 45-minute lesson on alkane nomenclature. Check it out! 

The Basics:

            There are several different alkyl groups, but there’s good news: they follow the same naming convention as alkanes but with one slight difference. For example, let’s say we’ve got a two-carbon chain. As a standalone molecule, we’d call that ethane. Eth indicates how many carbon atoms there are in the chain, and –ane specifies that it’s an alkane. As a substituent, however, it would be called ethyl. The –yl indicates that it’s a substituent of a larger molecule (or that it’s missing a hydrogen). 

Common Alkyl Groups:

            I’ve gone ahead and drawn methyl, ethyl, both propyls, and all butyls in bond line (skeletal structure) in blue below. I've also provided the condensed structures of the substituents. The cyclohexane just serves as a parent molecule :) Once we get into three-carbon substituents, we actually run into branched substituents:

Methyl, Ethyl, and Propyl:


MethylcyclohexaneMethylcyclohexane

The methyl substituent has just one primary carbon. Its condensed structure is —CH3.

EthylcyclohexaneEthylcyclohexane
The ethyl substituent has primary and secondary carbons. Its condensed structure is —CH2CH3.

PropylcyclohexanePropylcyclohexane

The straight-chain propyl substituent has primary and secondary carbons. Its condensed structure is —CH2CH2CH3.

IsopropylcyclohexaneIsopropylcyclohexane

The isopropyl substituent has primary, secondary, and tertiary carbons. Its condensed structure is —CH(CH3)2.

The Butyls:


N-ButylN-Butyl

The straight-chain butyl has only primary and secondary carbons in it. Its condensed structure is —CH2CH2CH2CH3.


IsobutylcyclohexaneIsobutylcyclohexane

The isobutyl substituent has primary, secondary, and tertiary carbons in it. Its condensed structure is —CH2CH(CH3)2.


Sec-butylcyclohexaneSec-butylcyclohexane

The sec-butyl substituent has primary, secondary, and tertiary carbons in it.  Its condensed structure is —CH(CH3)CH2CH3

Tert-butylcyclohexaneTert-butylcyclohexane

The tert-butyl substituent has three primary carbons and one quaternary carbon. Its condensed structure is —C(CH3)3.

I hope this quick introduction helps! To see my videos explaining all of alkane nomenclature, including alkyl groups, click here. Good luck studying! 


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.