** Shares of chemical maker Huntsman Corp HUN.N down 8.4% at $15.89 premarket

** Chemical firm Olin OLN.N will acquire HUN in an all-stock deal

** Offer price of $13.85 per share is about 12.8% below Huntsman's last closing price

** That gives the deal a value of $2.43 billion, according to Reuters calculation

** Under the terms of agreement, Huntsman shareholders will receive 0.5476 Olin shares for each share they own

** Transaction is expected to close in the first half of 2027

** As of last close, shares up 58.9% YTD