User:Wppreen/Chemical synthesis

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Green chemistry enables chemists to sustain the environment by reducing by-products and using more efficient reactions.

Strategies

Many strategies exist in chemical synthesis that are more complicated than simply converting a reactant A to a reaction product B directly. For multistep synthesis, a chemical compound is synthesised by a series of individual chemical reactions, each with its own work-up. For example, a laboratory synthesis of paracetamol can consist of three sequential parts. For cascade reactions, multiple chemical transformations occur within a single reactant, for multi-component reactions as many as 11 different reactants form a single reaction product and for a "telescopic synthesis" one reactant experiences multiple transformations without isolation of intermediates. Divergent synthesis allows a common intermediate to produce many compounds, whereas convergent synthesis combines different products synthesized through distinct chemical routes to yield a complex product. One-pot synthesis involves multiple reactions occurring sequentially in the same reaction vessel without the need for intermediate isolation. Additionally, strategies like photoredox catalysis offer finer control over the activation of small molecules and regulation of the oxidation state of metal catalysts, which has important applications in inorganic chemistry. Biocatalysis is a strategy employed by the body that speeds up chemical reactions using enzymes. Techniques such as flow chemistry enhance chemical synthesis by running reactions in a continuous stream, allowing the production of drugs like Tamoxifen (Breast Cancer) and Artemisinin (Malaria) [1].

Green Chemistry

Green Chemistry makes new chemical reactions that improve chemical synthesis by increasing the efficiency of resources and energy, making products more selective, simplifying processes, and protecting the environment. Atom economy is a technique that determines how efficient chemical processes are by maximizing the formation of products from starting reagents and decreasing side products. Atom economy allows chemists to reduce waste and increase environmental sustainability.

Applying green chemistry techniques has made the isomerization more sustainable. For instance, the isomerizations of propargyl alcohols into conjugated carbonyl compounds follow an atom-economical approach to chemical synthesis. Green chemistry replaces the typical two-step stoichiometric reduction and oxidation process with ruthenium-catalyzed redox isomerization to form enones from propargyl alcohols, decreasing waste and increasing efficiency. The efficient total synthesis of adociacetylene B demonstrates the increase in sustainability and environmental health from the methods of green chemistry.

The direct conversion of C-H bonds in organic molecules into desired products, without unnecessary chemical conversions, also follows the methods of green chemistry by reducing synthetic steps and removing protecting group chemistry. Employing green chemistry leads to fewer resources and side products while conducting the reaction in milder conditions. For example, the formation of complex organic compounds by creating C-C bonds directly from various C-H bonds is simplified by innovations in transition-metal-catalyzed C-H activation and cross-dehydrogen coupling (CDC). This step calls for an efficient synthesis since pre-functionalization is unnecessary, and waste is heavily reduced. Likewise, CDC can directly transform (NH)-indoles and tetrahydroisoqinolines into complex alkaloids, and aryl C-H bonds can be cross-coupled to make arene-arene coupling products.