In the Laboratory
An Efficient Procedure for Microscale Synthesis of Semicarbazones Sangeeta Pandita,* Samta Goyal, Nadira Arif, and Sarita Passey Department of Chemistry, Zakir Husain College, J. L. Nehru Marg, New Delhi 110-002, India; *
[email protected] Semicarbazones are useful derivatives to identify and characterize carbonyl compounds (1, 2). The following experimental grinding procedure is useful in identifying several carbonyl compounds. Semicarbazide hydrochloride (100 mg, 1 mmole) and sodium acetate (100 mg) are placed in a mortar and ground with a pestle (Scheme I). After the mixture turns to liquid, a carbonyl compound (1 mmole) is added. Grinding is continued for several minutes until a smooth paste is formed. The crude semicarbazone separates on addition of cold water to the paste and is recrystallized from ethanol. The crystallized product is vacuum filtered using a glass funnel and a Willstätter nail (1). Complete drying occurs in ∼5 minutes. The melting point of the purified semicarbazones is compared to those found in the literature
(1–3). The following carbonyl compounds were converted to semicarbazones by the grinding procedure: benzaldehyde 2-nitrobenzaldehyde 4-nitrobenzaldehyde 2,4-dichlorobenzaldehyde 3-bromobenzaldehydenaphthalene-1-carbaldehyde 4-hydroxybenzaldehyde acetophenone 4-bromoacetophenone 4-nitroacetophenone 4-hydroxyacetophenone 1-acetylnaphthalene 2-butanone 4-methyl-2-butanone
O C H2N
N NH2 H ⭈HCl
2-pentanone
O
+
C H3C
OⴚNaⴙ
Semicarbazide hydrochloride (CAS #563-41-7) is harmful if swallowed, inhaled, or absorbed through skin. Protective lab equipment should be worn during the synthesis procedure.
grinding
O C R
Literature Cited
R'
1. Vogel, A. I. Text book of Practical Organic Chemistry, 4th ed.; ELBS: Longman, U.K., 1978. 2. Cheronis, N. D ; Entrikin, J. B.; Hodnett, E. M. Semimicro Qualitative Organic Analysis; Interscience Publishers: New York, 1965. 3. Kolb, V. M.; Stupar, J. W.; Janota, T. E.; Duax, W. L. J. Org. Chem. 1989, 54, 2341.
O R'
C C
R
N
N H
NH2
Scheme I. Reaction to form semicarbazones.
108
Journal of Chemical Education
Hazards
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Vol. 81 No. 1 January 2004
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www.JCE.DivCHED.org
