Mixer Design and Flow Rate as Critical Variables in Flow Chemistry Affecting the Outcome of a Chemical Reaction: A Review

Abstract

Flow chemistry offers several advantages for performing chemical reactions and has become an important area of research. It may seem that sufficient knowledge has already been acquired on this topic to understand how to choose the design of microreactor/micromixer and flow rate in order to achieve the desired outcome of a reaction. However, some experimental data are difficult to explain based on commonly accepted concepts of chemical reactivity and performance of microfluidic systems. In this mini review, we attempt to identify such data and offer a rational explanation of unusual results based on the supramer approach. We demonstrate that variation in flow regime (determined by mixer design and flow rate) can either improve or worsen the reactivity and lead to completely different products, including stereoisomers. It is not necessary to mix the reagents with maximum efficiency. The real challenge is to mix reagents the right way since at a too high or too low flow rate (in the particular mixer), the molecules of reagents are incorrectly presented on the surface of supramers, leading to altered stereoselectivity, or form tight supramers, in which most of the molecules are located inside the supramer core and are inaccessible for attack, leading to low yields.

Diacetyl strategy for synthesis of NHAc containing glycans: enhancing glycosylation reactivity via diacetyl imide protection

“…Myachin and Kononov reviewed the influence of reactor shape and flow rate on the efficiency and selectivity of reactions based on the formation of supramers and their dynamic behavior ( Myachin and Kononov, 2023a ; Myachin and Kononov, 2023b ). In the Kdo glycosylation mentioned above, despite the absence of amide groups in the substrates, the efficiency of the glycosylation reaction increased when using a microflow reactor ( Figure 1 ).…”

“…On the other hand, glycosylation reactions are conducted in a homogeneous reaction system in organic solvents under dry conditions. However, as pointed out by Kononov et al, protected sugar derivatives may not be uniformly dispersed in solution; instead, they often tend to form clusters because of interactions such as intermolecular hydrogen bonding ( Kononov, 2015 ; Kononov et al, 2017 ; Podvalnyy et al, 2017 ; Orlova et al, 2017 ; Nagornaya et al, 2018 ; Myachin and Kononov, 2023a ; Myachin and Kononov, 2023b ). Microflow mixing of glycosyl donor and/or receptor clusters can afford a non-equilibrium mixing state similar to well-dispersed biphasic mixture.…”

Enhanced Effluent Degradation with Zinc Oxide, Carbon Nitride, and Carbon Xerogel Trifecta on brass monoliths

“…A negligible Peclet number (Pe << 1) indicates insufficient diffusion of reactants to the catalytic surface, limiting the reaction rate. Meanwhile, a very high Peclet number (Pe >> 1) represents a high influence of advection that may hinder the interaction between reactants and the catalyst (Myachin et al 2023). Another important parameter in flow processes is the dimensionless Reynolds number (Re).…”

Optimization of G1 Micromixer Structure in Two-Fluid Mixing Based on CFD and Response Surface Methodology

“…The flow in the microchannel is pumped or delivered with the limited velocity (≤m/s), resulting in a laminar state of low Reynolds number [4]. Therefore, molecular diffusion is the dominant mass transfer process in a micromixer [5];…”