Elucidating Structures Determine the molecular weight (Mass Spectrometry) and, if possible, the molecular formula and number of double bond equivalents. Look for the presence of characteristic functional groups in the IR spectrum. Make a list of chemical shifts for all the carbon atoms present in the molecule using the 13C NMR spectrum. Use the HSQC spectrum to determine the chemical shift of the protons attached to these carbon atoms. Look for spin systems present in the molecule using the COSY and TOCSY spectra. Corroborate this spin systems and establish the connection between them with the aid of the HMBC spectrum. Determine stereochemistry if possible with the help of coupling constant values and/or NOESY spectrum. Propose your structure.

(+)-ESI C17H22O2 (-)-ESI

Number of double bond/ring equivalents The number of double bond equivalents (R) is given by the equation: Where: a is the number of tetravalent atoms (C, Si) b is the number of monovalent atoms (H, Cl, Br, …) d is the number of trivalent atoms (N,P) (the number of divalent atoms (O,S) does not play a role here).

Chemical Shift Data

13C NMR Chemical shifts

Couplings of aromatic protons Aromatic protons couple to each other with coupling constants whose values depend on the relative position between protons.

Long range couplings Allylic and homoallylic protons couple to each other with a coupling constant of values 0-3 Hz. Protons related to each other by a “W planar geometry” are coupled with variable values of J. In general, protons that are part of a planar system have spin-spin coupling of a certain magnitude.

Two-dimensional correlation experiments

CD3OD CD3OD Alifáticos Dobles enlaces/Aromáticos Unido a O?

Aromáticos/doble enlace Alifáticos Carbonilo