Method

Difference (gauche to syn)

Barrier (syn to gauche)

B3LYP/6-311++G(3df,3pd)

157

1208

B3LYP/aug-cc-pV(T+d)Z

117

1161

CAM-B3LYP/6-311++G(3df,3pd)

180

1167

CAM-B3LYP/aug-cc-pV(T+d)Z

149

1123

M06-2X/6-311++G(3df,3pd)

211

1186

M06-2X/aug-cc-pV(T+d)Z

186

1164

MP2/6-311++G(3df,3pd)

225

1316

MP2/aug-cc-pV(T+d)Z

191

1234

CCSD/aug-cc-pVDZ

132

1239