... C. Dix a , Caroline S. Widdowson a and David Kipling * b a School of Chemistry, Main Building ... ES refers to electrospray ionization, CI refers to chemical ionization (ammonia) and EI refers to electron ionization. ... 6′-H), 7.62 (2H, m, 3′,5′-H), 4.92 (3H, br s, NH 2 and 4-H), 1.41 ...