ch 13 Flashcards
(23 cards)
The frequency at which a particular carbon atom appears in the ¹³C NMR spectrum is called the
chemical shift
3
5
1
An electronegative group attached to a carbon atom will ______ the electron density around the atom shifting the ¹³C NMR peak _______.
decrease; downfield
III
III
An ethyl group (CH₃CH₂-) that is attached to a quaternary carbon has what splitting pattern in a NMR spectrum?
A triplet and a quartet with relative intensities of 3 and 2, respectively.
IV
IV
“3 0” code
“6 1” code
“9 0” code
3 2 or 2 3 cross
Determine if hydrogens are homotopic, diastereotopic, enantiotropic, or unrelated
Type 1: Hydrogens are coming off same carbon
- replace 1 hyd with dutarium and count chiral centers
1. homotopic if ZERO chiral centers
2. enantiotropic if ONE chiral center
3. diastereotopic if TWO or MORE chiral centers
Type 2: Hydrogens are coming off different carbons
- unrelated UNLESS…
1. if HYDROGENS are symmetrical to each other then run Type 1
DEPT-90 tells us about
CH groups
+ DEPT-135 tells us about
CH and CH3
- Dept-135 tells us about
CH2
C=O has a chemical shift of about
220 - 160
C=C has a chemical shift of about
150 - 110
CH3 has a chemical shift of about
25 - 10
CH2 has a chemical shift of about
50 - 25
aromatics have a chemical shift of about
140 - 110
