In a bowl combine the flour, sugar, cocoa, baking soda and salt. Combine the orange juice, water, oil, vinegar, and vanilla. Stir into the dry ingredients just until moistened. Fold in chocolate chips. Coat muffin cups with nonstick cooking spray or use paper liners. Fill half full with batter. Bake at 375 for 13-16 minutes or until a toothpick comes out clean. Cool for 5 minutes before removing from panto a wire rack to cool completely. Just before serving, sprinkle with confectioners sugar.