video tutorial Semicarbazide from the reduction of nitrourea

Name: video tutorial - Semicarbazide from the reduction of nitrourea
Uploaded: 2025-12-11T09:03:44.112Z
Duration: 14 min 59 s
Description: in a previous video we prepared nitro urea today we're going to take this

Goal: reduce nitro urea to semicarbazide (a hydrazine derivative) via zinc/HCl under cryogenic conditions to preserve intermediates.
Starting materials: nitro urea (10 g) and zinc powder (25 g) with 75 mL of 36% hydrochloric acid; reaction requires keeping temperature below 0 °C.
Experimental setup: cooled reaction vessel with ice/salt bath, gradual addition of nitro urea in acid to a pre-chilled zinc/ice suspension; temperature monitored; slow addition over time.
Mechanism: reduction proceeds via unstable nitroso/intermediate species, with excess reducing agent and low temperature favoring formation of the hydrazine derivative (semicarbazide).
Observations: hydrogen gas evolution; temperature control essential; zinc gradually dissolves; reaction addition completes over several hours.
Workup: saturate mixture with salt to aid crystallization; filter solids; filtrate expected to contain product but separation is difficult.
Isolation: add cyclohexanone (9 g) to filtrate to form an adduct; crystallize after 24 hours.
Result: just over 2 g of off-white crystals obtained; ammonia treatment to remove zinc chloride yields cyclohexanone semicarbazone as an insoluble solid (<1 g).
Overall crude yield: about 6% starting from nitro urea.
Melting point test: observed mp around 151–154 °C, lower than literature ~165 °C, indicating impurities; recrystallization suggested.
Conclusion: the reaction is interesting but difficult to optimize due to cooling/reduction constraints; small amount of product obtained.