Introduction


The research conducted with Dr. Bradley for the spring term 2014 was focused on identifying unexplained electrochemical behaviors and anomalies. The whole series of experiments was designed to segway in to the collection of evidence regarding origins of life. This had two fundamental approached: 1) to determine if electrochemistry could be responsible for the formation of amino acids or similar species that would be consistent with the chemistry found on Saturn’s moon, Titan [1]; And 2) to identify any self-organizing behavior within these systems.

The first of such experiments examined the behavior of an applied electric field in organic media in the absence of supporting electrolyte. Typical electrochemical methods use an electrolyte in solution that supports the flow of electrons. These experiments, on the other hand, were designed to potentially discover a new realm of chemistry by using unexplored electrochemical methods. This was to be done on a low-voltage as well as a high voltage scale. However, the untimely conclusion of the project resulted in only low voltage measurements.


Experimental Summary


CRSEXP046 acetonitrile in applied electric field via copper wire electrodes
CRSEXP047 acetonitrile in applied electric field via copper wire electrodes
CRSEXP048 acetonitrile in applied electric field via copper plate electrodes
CRSEXP049 acetonitrile in applied electric field via graphite electrodes

The first experiment, CRSEXP046, examined an electrochemical system of pure acetonitrile exposed to a 23.5V potential via two copper electrodes at a separation of 4.5mm for 20 minutes. The current was below the detection limit of the power supply’s meter. A black precipitate formed at the cathode over the course of the experiment. This precipitate was < 0.001g in yield and was not soluble in any organic or aqueous solution. HNMR of the supernatant liquid showed no detectable change from the pure solvent.

The second experiment, CRSEXP047, was conducted similarly to the previous one with a few improvements. 1) A digital multimeter was wired into the circuit to measure the current, which was below the detection limit of the previous current meter. 2) The precipitate was allowed to form a bridge between the electrodes. Again, the precipitate was <0.001g and insoluble. Because of this, no characterization experiments were preformed.

In order to attempt to produce enough of this precipitate for characterization a new cell design was created in CRSEXP048. The new cell used two 24cm^2 copper plates at a 1mm separation with a capillary wick. 23.5V was applied across the plates. After about three minuets, the current spiked, suggesting that a bridge or multiple bridges formed between the plates.

To determine if the copper electrodes were contributing to this precipitate formation, the same experiment was conducted with graphite electrodes in place of the copper (CRSEXP049). The 23.5V was applied in the acetonitrile and a very minimal current was observed. No precipitate was observed. This suggests that the formation of this precipitate was contingent on the evolution of the copper ions into solution.


Results and Discussion


The electrochemistry of acetonitrile in the absence of electrolyte was still able to support minimal currents with both copper and graphite electrodes. However, the current produced by the copper electrodes was about two orders of magnitude larger than that produced by the graphite. In addition, the use of copper electrodes evolved a black precipitate that was not present with the use of graphite. This finding suggests that the copper contributes to the formation of this black precipitate.

Copper is a non-inert electrode. As the current begins to flow, copper ions will begin to evolve into solution via the cathode [2]. However, in the absence of an electrolyte, the reduction reaction at the anode needs to be investigated.

Though there was not enough of the black precipitate recovered for characterization, speculations about this chemistry can be made from previous experiments using similar systems.

It has been shown that copper ions are capable of coordinating with acetonitrile. The acetonitrile, as a ligand, can coordinate at up to three sites on the copper ion [3]. This would form the species Cu(AN)+, Cu(AN)2+, and Cu(AN)3+. While the formation of these species with copper electrodes in acetonitrile is plausible, this would only explain the cathode chemistry. In addition, copper complexes with weak ligands are known to be weak absorbers; thus, making it difficult to quantify this behavior using spectrophotometric methods [3].

The precipitate formed at the copper anode was highly colored and specific to the anode region. The lack of copper ions in this region suggests that this product is not related to any metal coordination chemistry. However, electrochemistry of other nitriles has demonstrated film formation also. One experiment proposed two mechanisms for polymer formation at the site of a platinum anode [4]. These mechanisms are shown in figure 1 and 2. This type of chemistry is plausible for the anodic site for the acetonitrile system in the experiments.

Andrew Buss Spring 2014-1.png
Figure 1. A proposed mechanism of the nitrile polymerization at the anode [4]


Andrew Buss Spring 2014-2.png
Figure 2. A second proposed mechanism of the nitrile polymerization at the anode [4]

The much lower current obtained with the graphite electrodes is expected because of the inert nature of graphite. However, with no supporting electrolyte and no apparent formation of products at either electrode, there is no evidence of what could be supporting this flow of electrons. An experiment by Stephanie C. Doan at the University of California investigated the phenomenon of solvated electrons in acetonitrile [5]. However, this system contains an iodide electrolyte which is inconsistent with the design of the CRS experiments.


Conclusion

While most electrochemistry is preformed in the presence of a supporting electrolyte, these experiments were done in the absence of electrolyte in an attempt to discover new electrochemistry. According to mainstream electrochemistry, the flow of electrons in absence of electrolyte is no possible. However, these experiments show minute currents are possible without an electrolyte in pure acetonitrile. When using copper as the electrode a precipitate was formed. This was evidence that the system was able to generate its own supporting chemistry at a 23.5V potential. Though the quantities of product that these supporting reactions produced was too small for characterization, it was thought to be supported by a polymerization at the anode as shown by C. Bureau. This product was not observed with the graphite electrodes. This was likely due to the lack of current these electrodes produced.



References


[1] https://www.youtube.com/watch?v=jeMwy3xuEs8

[2] I.D. MacLeod, A.J. Parker, and P.Singh. Electrochemistry of Copper in Aqueous Acetonitrile. Journal of Solution Chemistry 1981. 10(11), 757-774.

[3] P. Kamau and R. B. Jordan. Complex Formation Constants for the Aqueous Copper(I)-Acetonitrile System by a Simple General Method. Journal of Inorganic Chemistry 2001. 40, 3879-3883.

[4] C. Bureau, et al. First Attempts at an Elucidation of the Interface Structure Resulting From the Interaction Between Methacrylonitrile and a platinum anode: An Experimental and Theoretical (ab initio) Study. Surface Science 1996. 355, 177-202.

[5] S.C Doan and B.J. Schwartz. Ultrafast Studies of Excess Electrons in Liquid Acetonitrile: Revisiting the Solvated Electron/Solvent Dimer Anion Equilibrium. The Journal of Physical Chemistry 2013. 117, 4216-4221.