Conditions for Pd/C reduction of alkene

Question

I am trying to do a $\ce{H2}$ reduction of cyclic alkene (otherwise simple hydrocarbon with 1 methyl group along with the chain about the weakly-strained cycle) using $\ce{Pd/C}$, the cycloalkene neat, and some glacial acetic acid. I am starting with a $\ce{N2}$ atmosphere, and charging the vessel (Parr) with high pressures of $\ce{H2}$ $(\gt \pu{400 psi})$ and from ambient to elevated temperatures $(\pu{150 ^\circ C})$.

But the reaction isn't working (GC data only)... What am I overlooking? Or doing wrong? (I'm a chemist, but have never done this).

Could I be reducing the $\ce{N2}$, producing $\ce{NH3}$ and poisoning the $\ce{Pd}$? Am I sintering the $\ce{Pd}$ by adding too much $\ce{H2}$ too quickly or heating too high? Simply a slow reaction and I'm been impatient (running $\gt \pu{100 h}$ though)?

Answer 1

Catalytic hydrogenation is a fundamental reaction, specifically in organic chemistry (Ref.1). Yet, the reduction of multiple bonds using hydrogen gas $(\ce{H2})$ and a metal catalyst (e.g., $\ce{Pd/C}$) is a reaction familiar to all organic chemists. That is the same approach taken by OP in the reduction of cycloalkene to corresponding alkane in this question. However, OP has not given detailed reduction condition(s) so that we cannot answer OP's specific questions (For example, no GC traces have shown, so we don't know whether some side reactions happened). Thus, I'd attempt to give a different approach, which does not require $\ce{H2}$ gas thus, no need to control pressure and can avoid hazardous conditions such as flammability.

For this method called catalytic hydrogen transfer reduction of carbon-carbon double bonds, a plethora of examples has been published Ref.2). It is important to note that variety of solvents (e.g., methanol, ethanol, isopropanol, etc.) can be used as hydrogen-donor in this method. In theory, any organic compound whose oxidation potential is sufficiently low can donate hydrogen in this method, of cause, in the presence of catalyst. Thus, the choice of donor is generally determined by the ease of reaction and availability (Ref.2).

Recently, in a study of catalytic transfer-hydrogenations of olefins, glycerol has been used as the hydrogen donor and solvent (Ref.3-5). A typical reaction is illustrated in following image:

In general procedure is given in Ref.3:

In a typical procedure, $\pu{0.50 g}$ of cyclohexene and $\pu{0.03 g}$ of (5 wt.%) $\ce{Pd/C}$ were added to a vial with $\pu{5 g}$ of glycerol (all purchased from Aldrich). The mixture was placed in a preheated oil bath and heated to $\pu{70 ^\circ C}$ after which it was magnetically stirred for $\pu{5 h}$. At the end of the reaction, the reaction mixture was cooled and extracted with $\pu{2 mL}$ of diethyl ether. Finally, the ether phase was analyzed by GC analysis using an HP-5 column ($\pu{30 m} \times \pu{0.25 mm}$, $\pu{0.25 \mu m}$ thick) to determine the conversion.

References:

1. S. Nishimura, In Handbook of Heterogeneous Catalytic Hydrogenation for Organic Synthesis; John Wiley & Sons: New York, NY, 2001.
2. Gottfried Brieger and Terry J. Nestrick, "Catalytic transfer hydrogenation," Chem. Rev. 1974, 74(5), 567-580 (ODI: https://doi.org/10.1021/cr60291a003).
3. Dorith Tavor, Sergay Popov, Christina Dlugy, and Adi Wolfson, "Catalytic transfer-hydrogenations of olefins in glycerol," Org. Commun. 2010, 3(4), 70-75 (ODI: Has not given).
4. Robert H. Crabtree, "Transfer Hydrogenation with Glycerol as H‑Donor: Catalyst Activation, Deactivation and Homogeneity," ACS Sustainable Chem. Eng. 2019, 7(19), 15845–15853 (ODI: https://doi.org/10.1021/acssuschemeng.9b00228).
5. Adi Wolfson, Christina Dlugy, Yoram Shotland, and Dorith Tavor, "Glycerol as solvent and hydrogen donor in transfer hydrogenation–dehydrogenation reactions," Tetrahedron Letters 2009, 50(43), 5951-5953 (ODI: https://doi.org/10.1016/j.tetlet.2009.08.035).