Ch 13 H-NMR Notes - Chem 360 Jasperse Ch. 13 Notes....

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Chem 360 Jasperse Ch. 13 Notes. Spectroscopy 3 The four facets of 1H NMR spectroscopy : 1. The number of signal sets (Section 13.6) The number of signal sets tells how many types of symmetry-unique hydrogen are present Symmetry-duplicate hydrogens give the same signal sets 2. The chemical shifts (where the signals appear) (Section 13.5) (Most complex facet) The chemical shifts reflect the chemical environment of each type of hydrogen a. Whether attached to an sp3 or and sp2 carbon b. What kind of functional groups might be attached to the carbon on which the hydrogen is attached. c. Whether attached to carbon versus to oxygen or nitrogen 3. The integration (size/area) of each signal set (Section 13.7) (Simplest facet, once you know how) The integrated area for each signal set reflects how many hydrogens are responsible. a. 3H CH 3 group (or 2H and 1H groups superimposed) b. 2H CH 2 group (or two nonequivalent 1H groups superimposed) c. 1H CH or OH group 4. The splitting (number of lines) in each signal set (Section 13-8) The splitting provides information about what is connected to a given carbon a. N lines N-1 “neighbor” H’s (when working from spectrum to structure) b. N neighbors N+1 lines (when predicting spectrum from structure) Summary of Steps in Beginner 1H NMR Interpretation: 1. If provided with a chemical formula, calculate how many elements of unsaturation are present This helps to put you on the alert for the presence of double bonds, rings, or aromatics 2. Count how many signal sets you have. This will tell you how many types of hydrogen-bearing carbons you have. Hydrogens attached to symmetry-equivalent carbons will give equivalent signals) Clean CH 3 or CH 2 signal sets will normally have reasonable shape symmetry If you have asymmetric looking signals, there is a good chance that two or more different signal sets may be overlapping 3. Check the integration of each signal set. 3H CH 3 group 2H CH 2 group 1H CH or OH group The above are true if there isn’t any accidental overlapping Clean CH 3 or CH 2 signal sets will normally have reasonable shape symmetry a. So, for example, if you have a nice symmetric 3H signal, conclude you have a CH 3 b. But if you have a complex, unsymmetric 3H, do not assume it’s really a CH 3 . Effective recognition and integration of signal sets can help you know how many CH 3 ’s and CH 2 ’s you have in your molecule 4. Check diagnostic “chemical shift” windows of the lines Use yes-or-no checklist regarding the presence of key functional groups Things can get more complicated if two or more functional groups are both affecting a common signal set. Chemical shift information can quickly tell you whether hydrogens are attached to arenas or
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 10

Ch 13 H-NMR Notes - Chem 360 Jasperse Ch. 13 Notes....

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online