p-Anisidine (Sigma Aldrich)

1-Fluoro-2-nitrobenzene (Sigma Aldrich)

Potassium carbonate (Fisher Scientific)

To a 100 mL quick fit conical flask was added a uniform mixture of p-anisidine (6.16 g, 50 mmol) and potassium carbonate (10.37, 75 mmol). 1-fluoro-2-nitrobenzene (7.05 g, 50 mmol) was pipetted evenly across the surface of the solid, then the mixture was brought up to 160°C with minimal stirring.* As the solid began to melt**, the stirring rate was increased, and the mixture was maintained at 160°C for 5 hours. After this time, the reaction was allowed to return to room temperature and left overnight. Water (50 mL) was then added to the reaction mixture, which was then poured over ice (approx. 500 g) resulting in a red precipitate. Once the ice had melted, the pH was adjusted to pH=6 using a small amount of concentrated hydrochloric acid***. The solid produced was dissolved into ethyl acetate (200 mL), transferred to a seperating funnel and washed with distilled water (4 x 200 mL).  The organic phase was isolated, dried with sodium sulphate, filtered, and evaporated to dryness to produce a black tar. The tar was dissolved in a minimum amount of hot hexane and hot filtered. Upon cooling**** the solid produced was isolated by vacuum filtration to afford 4'-methoxy-2-nitrodiphenylamine (8.25 g, 68%) as a red solid. 

*A conical flat bottomed flask fitted with a reflux condenser.  The temperature what controlled using the sensor on the hot plate.  Stirring was accomplished using a stirring bar, which was controlled from the hot plate.  The whole reaction was accomplished in the open air without the need of dry/inert conditions.

** Visual observation.

*** Universal indicator paper was used to monitor the change in pH to pH=6.

**** Cool to room temperature without an ice bath.

¹H-NMR (300 MHz, DMSO-d₆): δ 9.40 (s, 1H, Ar-NH), 8.11 (dd, J = 8.6, 1.3 Hz, 1H, Ar-H), 7.45 (t, J = 7.8 Hz, 1H, Ar-H), 7.27 (d, J = 8.8 Hz, 2H, Ar-H), 7.02 (d, J = 8.8 Hz, 2H, Ar-H), 6.97 (d, J = 8.7 Hz, 1H, Ar-H), 6.79 (t, J = 7.7 Hz, 1H, Ar-H), 3.79 (s, 3H, O-CH₃). ¹³C-NMR (75 MHz, DMSO-d₆): δ 157.66, 144.19, 136.55, 132.59, 131.83, 127.34, 126.60, 117.39, 116.39, 115.22, 55.74. IR (ATR): 3328, 3007, 2960, 2837, 2322, 2115, 1903, 1615, 1565, 1496, 1437, 1402, 1347, 1323, 1298, 1265, 1244, 1222, 1168, 1142, 1109, 1072, 1030, 851, 809, 772, 742, 695. GC-MS (EI) m/z: 244.00 ([M]⁺). 

Casimero, C., McConville, A., Fearon, J.-J., Lawrence, C.L., Taylor, C.M., Smith, R.B., Davis, J. Sensor systems for bacterial reactors: A new flavin-phenol composite film for the in situ voltammetric measurement of pH (2018) Analytica Chimica Acta, 1027, pp. 1-8.