If someone could please give me the hint to how the initial attack is carried out, it'd be a huge help.
From the article by van Asselt and van Krevelen :
- Cyclohexanol is oxidized to cyclohexanone.
- The cyclohexanone reacts with the nitrous acid to yield isonitrosocyclohexanone producing 2-nitro-2-nitrosocyclohexanone by reaction with nitric acid.
- With attendant ring opening and uptake of water the latter compound is transformed into 6-hydroxyimino-6-nitro hexanoic acid.
- More than 90% of it is converted to adipic acid.
- van Asselt, W. J.; van Krevelen, D. W. Preparation of Adipic Acid by Oxidation of Cyclohexanol and Cyclohexanone with Nitric Acid: Part I. Reaction Mechanism. Recl. Trav. Chim. Pays-Bas 1963, 82 (1), 51–67. DOI: 10.1002/recl.19630820107.