Pattern-spotting on the X-ray. Let the air location tell the story. Free air UNDER the diaphragm means a hollow viscus like a peptic ulcer has perforated; air in the MEDIASTINUM means the oesophagus has torn. This patient shows pneumomediastinum, so the leak is oesophageal.
Confirm with the triad: Boerhaave syndrome runs as vomiting, then chest pain, then surgical (subcutaneous) emphysema, the Mackler triad, with the V sign of Naclerio on the film. The trigger of a heavy meal followed by retching fits perfectly.
Eliminate: no foreign body was swallowed; a perforated ulcer would give pneumoperitoneum, not pneumomediastinum; a ruptured bulla gives a pneumothorax in a COPD patient. So the answer is spontaneous oesophageal rupture. Ref: Bailey and Love, Short Practice of Surgery, 27th edition, 2018; SRB's Manual of Surgery, 4th edition.