7.4: Question 7.5.2.1 PASS - naming cycloalkane structures
- Page ID
- 452330
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Give the IUPAC names for the following cycloalkane structures.
- Answer
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a) 1,3-Dimethylcyclohexane
b) 2-Cyclopropylbutane
c) 1-Ethyl-3-methylcyclooctane
d) 1-Bromo-3-methylcyclobutane
e) 1,2,4-Triethylcycloheptane
f) 1-Chloro-2,4-dimethylcyclopentane
- Strategy Map
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Step Hint 1. Identify the longest chain (making up the ring or attached to it). Recall LibreText 7.5.2 Naming Cycloalkanes (see section IUPAC Rules for Nomenclature) 2. Count the number of carbons in the ring and along the carbon chains. 3. Number the connecting chains/rings based on alphabetical order. Ensure that you number each connecting chain going along the path that allows for the lowest numbers (this can be either left or right).
- Solution (parts b, c, d and f)
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b) The longest carbon chain is in the form of a four-carbon long chain.
Attached to the second carbon of the chain is a three-carbon long ring.
Answer 2-Cyclopropylbutane
c) The longest chain is a eight-carbon long ring.
Attached to the first carbon on the ring is a 2-carbon long chain.
Attached to the third carbon in the ring is a one-carbon long chain.
Answer 1-Ethyl-3-methylcyclooctane
d) The longest chain is a four-carbon long ring.
Attached to the first carbon on the ring is a bromine.
Attached to the third carbon on the ring is a one-carbon long chain.
Answer 1-Bromo-3-methylcyclobutane
f) The longest chain is a five-carbon long ring.
Attached to the first carbon on the ring is a chlorine atom.
Two one-carbon long chains are attached on carbons two and four of the ring.
Answer 1-Chloro-2,4-dimethylcyclopentane
- Guided Solution
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Download Guided Solution as a pdf
Guided Solution Hint This is a theory type problem where you will need to be able to name different types of cycloalkanes. See LibreText 7.5.2 Naming Cycloalkanes Question: Give the IUPAC names for the following cycloalkane structures. (parts b, c, d and f)
How to name cycloalkane structures:
- Find which chain is the longest. This can either be inside of the ring or attached to the outside, but you cannot count inside to outside or vice versa.
- This part will go at the end of the name.
- Identify your connecting chain(s)
- These will be named and numbered based on their order in the alphabet.
- If you have two of the same chains attached to separate carbons on the main chain, they will be listed in order of number (ex, -1, 3-methyl)
Recall the names for your carbon chains:
- 1 = methane
- 2 = ethane
- 3 = propane
- 4 = butane
- 5 = pentane
- 6 = hexane
- 8 = octane
- 9 = nonane
- 10 = decane
- If it is a ring, just put “cyclo” in front.
Complete Solution:
b) The longest carbon chain is in the form of a four-carbon long chain. (butane)
Attached to the second carbon of the chain is a three-carbon long ring. (2-cyclopropyl)
Answer 2-Cyclopropylbutane
c) The longest chain is an eight-carbon long ring. (cyclooctane)
Attached to the first carbon on the ring is a 2-carbon long chain. (1-ethyl)
Attached to the third carbon in the ring is a one-carbon long chain. (3-methyl)
Answer 1-Ethyl-3-methylcyclooctane
d) The longest chain is a four-carbon long ring. (cyclobutene)
Attached to the first carbon on the ring is a bromine. (1-Bromo)
Attached to the third carbon on the ring is a one-carbon long chain. (3-methyl)
Answer 1-Bromo-3-methylcyclobutane
f) The longest chain is a five-carbon long ring. (cyclopentane)
Attached to the first carbon on the ring is a chlorine atom. (1-Chloro)
Two one-carbon long chains are attached on carbons two and four of the ring. (-2,4-methyl)
Answer 1-Chloro-2,4-dimethylcyclopentane
Check your work!
To check if your answer, look back to ensure you followed all of the rules and guidelines. If you accurately named the compound, you should be able to redraw it using your name. The compound you draw should match the original molecule. If it does not, you know you made an error in your naming process.
Why do these answers make chemical sense?
To answer this question you have followed the IUPAC rules for naming cycloalkanes. Key is to make sure your longest chain is the parent part of the name. The longest chain may be a straight chain alkane with the cylcoalkane a substituent. If you focus on identifying the longest chain first and number your carbons to end up with the lowest possible substituent numbers then you have followed the correct approach.
See LibreText 7.5.2 Naming Cycloalkanes (see section IUPAC Rules for Nomenclature)
(question source from page titled 4.1: Naming Cycloalkanes Exercise 4.1.1 https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Organic_Chemistry_(Morsch_et_al.)/04%3A_Organic_Compounds-_Cycloalkanes_and_their_Stereochemistry/4.01%3A_Naming_Cycloalkanes, shared under a CC BY-SA 4.0 license, and was authored, remixed, and/or curated by Jim Clark, Steven Farmer, Dietmar Kennepohl, Zachary Sharrett, Layne Morsch, Krista Cunningham, Tim Soderberg, Pwint Zin, & Kelly Matthews)
- Find which chain is the longest. This can either be inside of the ring or attached to the outside, but you cannot count inside to outside or vice versa.