Dow Chemical is breaking off a significant part of its chlorine operations — including those in Plaquemine — in a deal with Olin Corp. valued at $5 billion.

Olin owns a plant in St. Gabriel.

Dow has been under pressure from hedge fund Third Point LLC to split its specialty chemical and petrochemical businesses.

Dow CEO and Chairman Andrew Liveris said in a statement that the Olin deal has helped the Midland, Michigan-based company exceed its target to divest $7 billion to $8.5 billion of non-strategic businesses and assets.

Dow’s stock climbed nearly 3 percent to $47.76 Friday, while Olin’s stock jumped 14 percent to $31 a share.

Dow said it would join its chlor-alkali and downstream derivatives businesses with Olin Corp. in a cash-and-stock transaction. The transaction includes Dow’s U.S. Gulf Coast chlor-alkali and vinyl, global chlorinated organics and global epoxy businesses.

Securities and Exchange Commission filings show the chlor-alkali and chlor-vinyl businesses and chlorinated organics business in Plaquemine are included in the deal.

Dow officials locally and at its headquarters did not respond to requests for comment.

In December 2013, Dow said chlor-alkali and chlor-vinyl facilities in Plaquemine were among manufacturing units that the company planned to sell or spin off along with most of its chlorine business.

The company also had said other Plaquemine facilities on the block included the chlorinated organics facility, the brine operations and select assets supporting it, and energy operations. The local plants employ about 300 people.

At the time, a state official said workers likely would become employees of a buyer.

Olin’s St. Gabriel plant employs more than 150 people, including 100-plus Olin employees and more than 50 contractors. The plant produces caustic soda, chlorine, hydrogen and sulfuric acid used in pulp and paper, textiles, pharmaceuticals, food processing and semiconductors.

The deal reported Friday includes $2 billion of cash and cash equivalents to be paid to Dow, an estimated $2.2 billion in Olin common stock and about $800 million of pension assumptions and other liabilities.

The new company will have annual revenue of nearly $7 billion.

Shareholders of Dow Chemical Co. will receive about 50.5 percent of Olin’s stock, with existing Olin shareholders owning about 49.5 percent.

Clayton, Missouri-based Olin said it anticipates annual cost savings of at least $200 million within three years. Joseph Rupp will remain as Olin’s CEO. Its board will include the existing nine Olin directors and three new members to be designated by Dow.

The deal, which is targeted to close by year’s end, still needs approval from Olin shareholders.

Dow and Olin also announced a separate, 20-year long-term capacity rights agreement for the supply of ethylene by Dow to Olin.