Does the largest known cycloalkane contain 288 carbon atoms?

Question

If you Google "largest known cycloalkane", you will find this result:

For context, there has been discussions on "largest known alkane":

• Largest alkane having a given alkane as its base name
• IUPAC nomenclature of extremely long alkanes

The Wikipedia article for cycloalkane mentions that the larger cycloalkanes, with more than 20 carbon atoms are typically called cycloparaffins. So, there has to be a known "cycloparaffin" with highest number of carbon atoms.

The above result came from a random HW-QnA site. From where does the result come from?

Question: Does the largest known cycloalkane really contain 288 carbon atoms? If not, how many carbon atoms are there in the largest cycloalkane that has been actually observed and isolated?

Answer 1

According to Makromol. Chem., Rapid Commun. 1985, 6 (3), 203–208^[1], Kwang Sup Lee and Gerhard Wegner, attempting the synthesis and study of $n>100$, $\ce{C_nH_{2n}}$ cyclo-alkanes and linear alkanes, were successfully able to synthesize a linear alkane of $\ce{C384H770}$ and cycloalkanes with 288 carbons ($\ce{C288H576}$)

Linear alkanes up to $\ce{C384H770}$, (2k; M = 5378) and cycloalkanes up to $\ce{C288H576}$(3g; M = 4040) were prepared by this strategy.

A brief method of preparation is as follows:

The strategy of the synthesis of long chain linear and cyclic alkanes was developed starting from the work of Schill et al. who had shown that the oligomers obtained by oxidative coupling of 1 following Eq. (1) can be separated by adsorption chromatography. \begin{align} \ce{\underset{\textbf{1}}{HC#C-(CH2)20-C#CH} ->[Cu^2+] \\ \underset{\textbf{2}}{HC#C-(CH2)20-C#C-\left[C#C-(CH2)20-C#C\right]_m-H}} \\ \end{align}

A similar strategy was used to synthesize the cycloalkanes as well.

The cyclic oligomers were synthesized by the same reaction according to Eq. (2) under conditions of high dilution of the terminal diacetylene

Finally, the linear and cyclic oligomers were hydrogenated over a Pd/C-catalyst in a conventional manner to obtain the analytically pure alkanes.

As for the assignment question, I was able to link it to a introductory exercise in Organic Chemistry by Janice Gorzynski Smith.².

Reference

1. Kwang Sup Lee, Gerhard Wegner, "Linear and cyclic alkanes ($\ce{C_nH_{2n+2}, C_nH_{2n}}$) with $n > 100$. Synthesis and evidence for chain-folding," Makromol. Chem., Rapid Commun. 1985, 6 (3), 203–208 (https://doi.org/10.1002/marc.1985.030060316)
2. Janice Gorzynski Smith, Organic Chemistry, Sixth Edition, McGraw-Hill book Company Inc.;2020, ISBN: 978-0-07-066720-4