Steps and mechanisms to synthesis of organic compounds

Transcription

1 Journal of Environment and Life Sciences J Environ Life Sci. September 2016; vol. 1 (Issue 1): ISSN Review Article Steps and mechanisms to synthesis of organic compounds Nagham Mahmood Aljamali Organic Chemistry, Chemistry Department, College of Education, Iraq For correspondence Dr. Nagham Mahmood Aljamali, Organic Chemistry, Chemistry Department, College of Education, Iraq. dr.nagham_mj@ya hoo.com Received: 05 July 2016 Accepted: 27 July 2016 ABSTRACT Various methods of chemical compounds were collected in this review article to interest them in synthesis of compounds as a procedures for preparation with their conditions. This review included more than one procedure for synthesis of various compounds, intermediates, steps and mechanism of reactions, conditions and catalysis. Many new compounds are synthesized to discover useful biological activity, and when activity is discovered, related compounds are synthesized to improve it. Syntheses suitable for production of drug candidate molecules are developed. Other compounds are synthesized to explore the mechanisms of biological processes. Then we sit down with a piece of paper and a pencil and propose a theory for how the reaction occurs, showing the transformation of starting material into products as a series of discreet steps, each of which produces a distinct intermediate compound or ion, called an "intermediate". Keywords: Mechanism, Procedures, Intermediate, Organic, Synthesis Introduction A major purpose of organic synthesis at the current time is the discovery, understanding, and application of biological activity. Pharmaceutical laboratories, research foundations, and government and academic institutions throughout the world are engaged in this research. 1-3 Many new compounds are synthesized to discover useful biological activity, and when activity is discovered, related compounds are synthesized to improve it. Syntheses suitable for production of drug candidate molecules are developed. Other compounds are synthesized to explore the mechanisms of biological processes. 4,5 1. A multi-step synthesis of any organic compound requires the chemist to accomplish three related tasks. 2. Constructing the carbon framework or skeleton of the desired molecule. Introducing, removing or transforming functional groups in a fashion that achieves the functionality of the desired compound. 3. Exercising selective stereo control at all stages in which centers of stereoisomerism are created or influenced. These are not discrete independent tasks to be attacked and solved in turn, but must be integrated and correlated in an overall plan. Thus, the assembly of the molecular framework will depend in part on the structure and functionality of available 8

2 starting materials, the selectivity (regio and stereo) of the various reactions that may be used to stitch them together, and the loss or relocation of functional groups in the intermediate compounds formed on the way to the final product. Other factors must also be considered, always in context with those listed above. 4. Since a successful synthesis must produce the desired product in reasonable amount, it should be as short and efficient as possible. A two or threestep sequence is usually better than a six or seven step procedure, even if the individual step yields are better in the longer route. Most reactions do not proceed in 100% yield, and the losses are multiplied with each additional step. Furthermore, a long multi-step synthesis requires many hours of effort by the chemists conducting the reactions. 6,7 Reactions of three components 8 Reactions of Two Components 5-8 Figure 1: Reactions of three components. Synthesis of compounds in presence of conditions

3 Figure 2: Synthesis of compounds in presence of conditions. Formation of cycles: 7,8 Figure 3: Formation of cycles. Acetanilide is prepared from aniline by acetylating it with acetic anhydride in the presence of glacial acetic acid. Aniline or phenylamine is a primary amine with molecular formula C 6H 5NH 2. It is basic in nature. Acetic anhydride is an anhydride of acetic acid and acts as a source of acyl group. Aniline reacts with acetic anhydride by nucleophilic substitution reaction. The reaction between aniline and acetic anhydride is called acetylation. In this reaction, aniline acts as the nuclepohile and acyl (CH 3CO- ) group from acetic anhydride acts as the electrophile. Here, the hydrogen atom of NH 2 group is replaced by the acyl group. The chemical reaction is shown below Mechanism of Dibenzal acetone Preparation It is prepared from benzaldehyde and acetone by Claisen-Schmidt Reaction. Claisen Schmidt Reaction is a condensation reaction between an aromatic aldehyde and an aliphatic ketone in the presence of a strong base like NaOH leading to unsaturated ketone. In this reaction, two molecules of water are eliminated. In the preparation of Dibenzal acetone, two moles of benzaldehyde condenses with one mole of acetone. The chemical reaction is represented as follows (10-13) ; Figure 4: Preparation of Dibenzal acetone. 10

4 Mechanism Including Rearrangement Some of reactions include (rearrangement, elimination, substitution, expansion, insertion of carbon atom or hetero atom) like : Figure 5: Rearrangement mechanism. Steps for synthesis of new organic compounds: Figure 6: Synthesis of new organic compounds. 11

5 Michael reaction (intra reaction): Dianions in synthesis: 18,19 We have discussed the regioselective reactions of this active methylene carbon (C-2) in ethylacetoacetate. Can regiospecifically trap C-4 via the dianion; Mannich reaction: Ring Expansion: by insertion 18,19 of carbine Figure 9: Dianions in synthesis. Or ring expansion by rearrangement: Conclusions There are many methods for synthesis compounds depend on type of reaction, type of product, condition and catalysis of reaction, medium of reaction. Funding: No funding sources Conflict of interest: None declared References Figure 7: Ring expansion. Or through unsaturated - position : Carbanions derived from active methylene compounds react with α,β-unsaturated compounds by 1,4-(conjugate) addition known as Michael addition. Figure 8: Michael reaction. 1. George S. Organic Chemistry. Mosby-Year Book; 1995: Sykes P. A gide Book to Mechanism in Organic Chemistry. 1974, 5th Ed, Longman. 3. Brewster RE, McEwen WE. Organic Chemistry, 30 ed; 1971: Marry BA. Organic Reaction Mechanism. Jon Willey sons; Fieser LF, Eilliamson KL. Organic Experiment, 5th Ed, Heath and company Toronto, Canada; 1983: Carey FA, Sundberg RJ. Advanced Organic Chemistry, Part A:strures and Mechanisms, 2 nd ed, Plenum Press. New York; 1983: Aljamali NM. As J Rech. 2014,7(9): Wilson CO, Givold O. Text book of Organic Medicinal and pharmaceutical Chemistry. 5th Ed, Pitman Medical Publishing Co. LTD, London, J. B. Lippin Cott Company;

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