HMX Cyclotetramethylenetetranitramine

HMX (7.10) is formed as a by-product during the manufacture of RDX by the Bachman process. 

Hexamethylenetetramine, acetic acid, acetic anhydride, ammonium nitrate and nitric acid are mixed together and held at 45 °C for 15 min. Ammonium nitrate, nitric acid and acetic anhydride are then slowly added and left on a steam bath for 12 h. A precipitate forms containing 27% RDX and 73% HMX. This process is shown in Reaction 7.16. 

RDX is destroyed by placing the precipitate into a hot, aqueous solution of sodium tetraborate decahydrate with a small amount of sodium hydroxide. The RDX is completely destroyed when the value of the pH increases to greater than 9.7. HMX is filtered and recrystallized from nitromethane to give the )5-form of HMX. 

Nitroguanidine (7.11) exists in at least two crystalline forms, the a- and -forms. 

The most common method of manufacturing ammonium nitrate is by injecting gaseous ammonia into 40-60% nitric acid at 150 °C as shown in Reaction 7.18  

---

In the Bachmann process an 80—84% yield is obtained, ca 10% of which is cyclotetramethylenetetranitramine (HMX). The Woolwich process gives a 70—75% yield containing only a trace of HMX. 

Cyclotetramethylenetetranitramine or HMX (C4H8N808) is a white crystalline solid with a melting point of 285°C. HMX is superior to RDX in that its ignition temperature is higher and its chemical stability is greater. However, its explosive power is... 

Oktoghen (Octogen or HMX). Designation for Cyclotetramethylenetetranitramine, described in Vol 3 of the Encycl, pp C605-R to C610-R. 

---