Creating Words in Chemistry

The need for new words or annotations to frame a concept or idea within the context of chemistry is as old as chemistry itself. From Catalysis and Chirality to Entgegen and Zusammen. The introduction of words or annotations has enabled a deeper understanding by aiding discussion and ultimately improving discourse. This is decidedly through the lens of a narrative bias; the words that remain are useful (or they wouldn’t survive) and are often well-defined, either from their inception or over the course of time (or they can’t be used effectively). However, there are often times when the introduction of these phrases is done poorly or not at all, and an emerging precedent of creating new terminology for the sake of rebranding an old concept. This isn’t always a bad thing, by labeling a new field of study, the attention shifts and creativity can flow into new directions. However, this needs to be done with scientific rigor or not at all.

C-H Activation

A strong case against introducing words without strict definitions is made by C-H activation. The phrase is used extensively within the literature but has become a parody with its definition changing from individual to individual, leading to confusion and overuse.

The definition broadly implies the “activation” of a strong C-H bond. However, this is used to describe a number of mechanistic pathways, from direct oxidative addition, HAT, simple deprotonation, and others all under one banner. No doubt due to the umbrella like definition, it is a useful shorthand and certainly makes it easier to hype a paper, especially since
C–H activation is a hot topic in synthetic chemistry.

The term’s frequent and sometimes imprecise use obscures important distinctions between reactions. The best way to use the phrase is in conjunction with the mechanisms involved; this ensures clarity within research discussions, but the precision is often dropped to introduce some air of mystery which is wholly unscientific.

My personal preferred definition relates to the direct oxidative addition of a C-H bond to a transition metal complex with an increase in the formal oxidation state of the metal by +2 and the generation of a M-C and M-H bond.¹ This is a precise definition that can be used in discussion with understanding between peers. This precision facilitates scientific discourse; however, because the definition is not universal, if I talk of C-H Activation and my peer has CMD present in their mind, our communication is broken. A repairable communication of course, but one that still takes time to address.

Another issue that seems to be creeping into the literature is the trend of introducing new words to increase the “impact” of a paper without explaining what this new word means or simply rebranding chemistry. This falls under hype and rarely adds strength to a paper. The chemistry should be able to speak for itself; a romantic notion, but it’s not an absurd one and in most papers, the chemistry is already speaking for itself. Grant writing is for hype, academic literature is for reporting.

Skeletal Editing

This is not a new branch of chemistry, it’s been known for quite a number of years.² However in 2021 it was rebranded by Levin.³ Initial skepticism around the rehashing of what look like ring expansion or rearrangement reactions has given way to the understanding that although known for centuries, the moniker of skeletal editing has brought attention to this interesting field. The reactions on the whole are different from rearrangements and the scope for genuinely interesting transformations only grows as more academics join the field.

Furthermore, the phrase introduced is simple and tangible. Within chemistry we use skeletal representations regularly, so the editing of such a structure is comprehensible from the get go. This has allowed for rapid uptake and largely the literature hasn’t strayed too far from the initial concept. Although a precise definition should be canonised before things get out of hand.

Transduction

On the other hand, Transduction reported by Silvi et al. in 2023,⁴ was presented in the title of the paper – in the same vein as Levin’s skeletal editing. However, the word transduction causes confusion because it has not been used ina chemical context and is not as intuitive as skeletal editing.

Transduction

noun

trans·​duc·​tion (tran(t)s-ˈdək-shən) 

: the action or process of transducing

transducing : to convert (something, such as energy or a message) into another form.

A quick google revealed that essentially it is the conversion of energy into another form. For example, sense organs transduce physical energy into a nervous signal; or a microphone transduces sound into an electrical pulse. So, in sum, has no relation to chemistry and is not easily intuitable from known contexts, so ideally should not be used in a title.

The text did not define transduction either, it has to be inferred from the work done. The hypothetical problem is that there is a polarity missmatch between electron rich radicals and electron rich alkenes. This kinetically inhibits coupling and so limits the scope of desirable functional groups.

To circumvent this problem, an electron poor alkene that would favour the initial coupling could be used and then displaced in a second step to form the desired product.

Figure 1. The hypothetical problem and it’s potential solution

Introduction of the polarity transducer – a rationally designed vinyl sulfonium salt – allows for this problem to be navigated. It is an elegant solution. But what is a polarity transducer? and by extension what is a transduction in chemistry? This leaves a lot of questions open and resolves few of them. Of course the understanding can be intuited by the user but as we have seen from C-H activation, this is not wise.

To come to a definition we first need to go up the pyramid of abstraction.⁵ The current paper is specific – vinyl sulfonium, SET, carboxylic acid. Thus we need to generalise the reaction:

A hypothetical synthon is replaced by a polarity transducer which allows for a classically unfavourable standard disconnection to be achieved through a two-step synthesis.

Figure 2. Generalised view of Polarity Transduction.

The general definition is never going to be perfect in the beginning, it needs to be refined and tested. Then retested to encompass an adaquate range of reactions but still be clearly and precisely defined. This is just a case study and one that I am using as a test bed for further development.

There are a number of criteria – especially with a new methodology, the defintions could touch on stoichiometry, mechanism, solution, potentially including specific reagents.

The reaction mechanism is one of the fundamental parts that build into a definition, the overall transformation may not be as important as the mechanism, or vice versa. Polarity transduction is orientated more towards generality – think photoredox – rather than a specific transformation, so the definition tends towards generalisation and the essential steps must be defined.

Since the definition is aiming for generality, it may not necessarily include specific mechanisms or reagents. In figure 3a, the first step is a polar addition of a thiol into a vinyl sulfone . This replaces an electronically unfavoured reaction with one that is kinetically and thermodynamically feesible. The second displacement of the transducer by a nucelophile may not be realistic, but the excercise here is to assess whether the reaction has to be SET based or can it also be polar in nature. It seems that the reaction satisfies the notion of a polarity transducer.⁶

Figure 3. The mechanism of reaction, doesnt seem to detract from the idea of a Polarity Transducer.

In figure 3b, we consider whether the reaction has to be purely organic or whether a dual catalytic scenario is within the definition. The use of acrylic acid as a polarity transducer creates a viable pathway for the reaction as a nucleophilic radical readily couples with the electronically inverted carboxylic acid. The second step would also satisfy the notion of a PT even if the mechanism uses dual catalysis as the transducer is replaced by a “general nucleophile” To this end, the definition does not need to include reference to its reaction mechanism. It doesn’t seem to matter if the reaction is SET, polar, dual-catalytic and by extension polarity transduction can include cycloadditions or other mechanistic scenarios.

From the analysis of these two hypothetic reactions, the following steps seem to be essential:

• One of the synthons must remain the same.
• The electronic nature of the polarity transducer must “flip the sign” of the reaction.⁷
• The polarity transducer must be displaced in the second step.

Whilst this is certainly not an exhaustive analysis of this work, and just a quick and dirty driveby, by providing more information on what a transducer is and why it deserves its name. People can more widely accept the reasoning behind why this new field is interesting or worth diving into. I tentatively suggest the following definition:

Polarity Transduction

A method in which an electronically mismatched reaction is facilitated through the replacement of one synthon with a “polarity transducer”. The transducer is the electronically inverted equivalent of the desired synthon which enables a two-step sequence: (1) the formation of an intermediate through an electronically favoured reaction followed by (2) the displacement of the transducer to yield the desired product.

Just as a note, this is not a critique on the work done, i think that it is an elegant design with an interesting premise. I like the paper, it is well executed. This is a critique on the approach to introducing new language into the chemistry vernacular.

The introduction of new terms into chemistry is an inherently powerful tool for shaping research and sparking creativity. However, without precise definitions or rigorous contextual framing, these terms risk becoming obstacles to understanding rather than vehicles for progress. The examples of “C-H Activation,” “Skeletal Editing,” and “Transduction” showcase both the potential and pitfalls of naming within chemistry. While terms like “Skeletal Editing” have successfully galvanized interest and research, others like “C-H activation” highlight the dangers of ambiguity. Whereas “transduction” has great potential, the lack of a strong definition has

Scientific communication thrives on precision. The chemistry community must balance the excitement of novel terminology with the responsibility to ensure its clarity, utility, and robustness. A poorly defined term may find itself diluted, overextended, or relegated to obscurity, taking with it the very ideas it sought to encapsulate.

This critique is not aimed at the creative efforts of researchers or their contributions to the field. As chemistry evolves and interdisciplinary fields burgeon, the precision of our language will remain pivotal to the advancement of science. A well-chosen word or annotation does more than name—it builds bridges across disciplines, fosters innovation, and ensures that chemistry remains an art of understanding as much as it is a science of transformation.

Footnotes