Suggest a synthetic route to heptane starting from 1,3 -dithiane and 1 -iodopropane. ANSWER Easy (and effective in practice). First do a double alkylation of the dithiane, then desulfurize with Raney nickel (p. 261). CC(C)(C)[SH]1CCCSC1

Double alkylation is a chemical reaction where two alkyl groups are introduced into a molecule in two separate steps. In this reaction, we start with 1,3-dithiane, which has two positions on its carbon chain that can react. By using a strong base, like n-butyllithium (n-BuLi), we deprotonate 1,3-dithiane, making it highly reactive. Then, we add two equivalents of 1-iodopropane. Each equivalent adds a propyl group to the carbon atoms adjacent to the sulfur atoms in the dithiane ring.
This transforms the original molecule into a 1,1,3,3-tetraalkylated dithiane, where now you have larger carbon chains attached to the ring system. Because this reaction is done twice (double alkylation), it is termed as such.
Understanding double alkylation is essential because it’s a fundamental step for forming more complex structures in organic chemistry.

Desulfurization is the process of removing sulfur atoms from a molecule. In our synthetic route, after performing double alkylation on 1,3-dithiane, the next step is desulfurization. By treating the alkylated dithiane with Raney nickel, the sulfur atoms in the dithiane ring are removed.
Raney nickel is a catalyst that helps in breaking the C-S bonds (carbon-sulfur bonds) efficiently. The breaking of these bonds and their replacement with C-H bonds (carbon-hydrogen bonds) results in the formation of a straight-chain hydrocarbon. For our particular reaction, the end product is heptane, a seven-carbon alkane.
This step is crucial because it transforms a thioketal (a compound containing sulfur) into a more straightforward alkane, simplifying the final product structure.

Raney nickel is a granular catalyst composed primarily of nickel, often supported by aluminum. It is widely used in organic chemistry for hydrogenation reactions and desulfurization processes.
In our synthesis, Raney nickel is employed to facilitate the removal of sulfur atoms from the alkylated dithiane. When we treat the tetraalkylated dithiane with Raney nickel, it causes the sulfur atoms to detach from the molecule. This happens through a process known as catalytic hydrogenation, where hydrogen atoms are added to the molecule, replacing the sulfur atoms.
Raney nickel is particularly efficient for such reactions due to its high surface area and the active sites that interact with the substrate. This makes Raney nickel an indispensable material in synthetic organic chemistry.

1,3-dithiane is an organic compound characterized by a six-membered ring containing two sulfur atoms at the 1 and 3 positions. This structure makes 1,3-dithiane a valuable building block in organic synthesis.
The sulfur atoms in 1,3-dithiane can stabilize carbanions formed at the adjacent carbon atoms, which are crucial intermediates in various reactions, including alkylation. In our synthetic route, we start with 1,3-dithiane and first double alkylate it with 1-iodopropane.
The reason 1,3-dithiane is so effective in synthetic chemistry is due to its ability to undergo these reactions cleanly and form stable intermediates, making it easier to conduct multi-step syntheses. Understanding how to manipulate 1,3-dithiane can unlock numerous pathways for creating more complex molecules.