Burger King Holdings Inc., America's perennially No. 2 hamburger chain, said Thursday that it is selling itself to little-known private equity firm 3G Capital in a deal valued at $3.26 billion. Its shares soared to an 18-month high. Thursday's $24-per-share tender offer comes after a day of speculation about the deal that sent shares up more than 15 percent. The offer is a nearly 46 percent premium over the company's stock price before rumors of a buyout began circulating. Under the terms of the deal with 3G, Burger King's Chairman and CEO John Chidsey will become co-chairman of the board. 3G Managing Partner Alex Behring will be the other co-chairman. Burger King, with its 12,100 locations around the world, lags its far larger competitor McDonald's Corp., and has struggled to keep up with its rival during the economy's rollercoaster of the past two years. Among the biggest problems: high unemployment among its most important, but notoriously fickle, group of customers: young men between 18 and 34. It's more than the bad the economy that's led to five consecutive quarters of declines in an important performance measure of sales at locations open at least a year. Burger King's once-unique concept of flame-broiled burgers isn't so rare any more, thanks to a boom in gourmet hamburgers from smaller competitors such as Five Guys, The Counter and In-N-Out Burger. And it's hard for Burger King to make solid profits while competing with McDonald's super-low prices. “McDonald's is just eating their lunch,” said Bob Goldin an analyst at the food consulting firm Technomic Inc. “Burger King's very heavily focused on a core audience of the younger male. And with that group, their attention goes to wherever has a better deal or whatever is hotter.” Burger King is based in Miami and became publicly traded in 2006, four years after a earlier consortium of investment firms acquired the company. The group - TPG Capital, Bain Capital Partners and Goldman Sachs Funds - still owns 31 percent of Burger King's outstanding shares and have agreed to tender their stock in the deal. 3G Capital, a six-year-old firm founded by Pavel Begun and Cory Bailey, has described its investment strategy in simple terms: buy businesses at a discount, hold onto them for long-term growth and don't get bogged down with quarterly results. While the New York company has a slew of partial or controlling holdings in South and Central American businesses, it hasn't made many huge waves - or fully bought out many corporations.