This offer would value Covestro at over EUR10 billion on the basis of its market capitalization, or up to EUR13.5 billion on the basis of its enterprise value - which includes net debt, long-term provisions and the pension plan.

Covestro's share price jumped on the announcement of the rumor, from EUR38 to EUR47. However, with a spread of 15%, it remains significantly lower than the price apparently offered by the Abu Dhabi National Oil Company, or ADNOC.

It is interesting to note that ADNOC is making an offer here that some would consider rather low. Covestro has generated an average of EUR1 billion in free cash flow per financial year over the last five years: the proposed price therefore represents a valuation of x13-x14 profits.

This does not appear unreasonable at first sight - it's what a financial investor concerned not to overpay for his acquisition would propose. However, it is highly likely that a strategic shareholder would have offered much more.

In this respect, some analysts estimate that ADNOC's offer represents a discount of at least 40% on the replacement value of Covestro's assets, estimated at around EUR90 per share.

The German group has been fairly successful in moving upmarket since its separation from Bayer at the end of 2015, even if it is not immune to powerful cyclical effects, which are inevitable in the chemical industry in general.

If its board of directors were to accept ADNOC's offer, it would certainly send an extremely pessimistic signal to investors positioned in the sector.