Term
| # of different H in molecule |
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Definition
| correspond to # if different signals |
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Term
| ratio of # of H atoms of each different type |
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Definition
| determined from ratio of areas under signals |
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Term
| hybridization of C atom that each H is attached to and/or presence of any highly electronegative atoms nearby in the structure |
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Definition
| determined from position of signal in HNMR spectrum (i.e. chemical shift) |
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Term
| # of neighboring, non-equivalent H atoms |
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Definition
| determined from splitting/multiplicity of each signal |
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Term
halomethanes (CH3-)
(i.e. CH3F) |
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Definition
*as electronegativity of halogen increases (F=most electronegative), electron density at H atom decreases
-H will be more deshielded-->chemical shift=greater
-Exs: CH3F=4.26 vs CH3Cl=3.05 |
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Term
| each different H atom in molecule gives rise to different signal |
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Definition
| happens because magnetic field at each different H atom=unique |
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Term
| position of signal in HNMR=characteristic of hybridization of C atom that H is attached to and/or presence of highly electronegative atoms nearby in structure |
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Definition
| these factors vary the induced magnetic field |
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Term
| greater the # of H atoms of each different type, the greater the amount of energy absorbed for that excitation |
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Definition
| intensity of each signal=proportional to # of H atoms of each type |
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Term
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Definition
*# of signals
*integration (measured by area under peaks)
*chemical shift
*splitting pattern (multiplicity) n+ 1
*coupling constants |
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Term
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Definition
-electrons shield atom's nucleus
-as shielding increases, magnetic field at nucleus decreases, so energy required to bring nucleus into resonance (flip spin) also decreases
-nucleus that's more shielded comes into resonance at lower frequencies |
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Term
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Definition
-upfield: to right-->shielded
-downfield: to left-->deshielded |
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Term
| shielding depends on 3 factors |
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Definition
1. electronegativity of nearby atoms
2. hybridization of adjacent atoms
3. magnetic induction w/in adjacent pi bonds
-increased shielding means upfield |
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Term
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Definition
-signal splitting tells about types of Hs on neighboring Cs
-degree of signal splitting determined by n+1
*if H has n Hs nonequivalent to it but equivalent among selves on same/adjacent C, it's HNMR signal split into n+1 peaks |
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Term
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Definition
-nonequivalent H's on the SAME carbon will couple to each other and cause splitting
-can be nonequivalent H's when there's restricted bond rotation (i.e. in alkenes or cyclic structures)
-geminal coupling constants=small-->0-5 Hz |
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Term
| alkenes: trans coupling vs cis coupling |
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Definition
-larger coupling constants for trans-->11-18 Hz
-smaller for cis-->5-10 Hz
-geminal=smallest-->0-5 Hz |
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Term
| determining # of signals from a structure |
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Definition
| count # of nonequivalent Cs/Hs |
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Term
| chemical shifts depend on: |
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Definition
-electronegativity of nearby atoms
-magnetic induction w/in adjacent pi bond |
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Term
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Definition
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Term
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Definition
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Term
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Definition
-distance btwn peaks in a split signal
value=measure of magnetic interaction of nuclei whose spins are coupled |
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Term
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Definition
HNMR--> .8-1.7
CNMR-->10-60 |
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Term
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Definition
HNMR-->4.6-5.7
CNMR-->100-160
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Term
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Definition
| OH groups don't have very distinctive chemical shifts |
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Term
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Definition
distinctive in HNMR spectrum
3.3-4.0 of Hs on C attached to ether oxygen |
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Term
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Definition
-aldehyde Hs at 9.5-10.1
-alpha Hs of aldehydes amd ketones ta 2.2-2.6
-CNMR-->carbonyl Cs at 180-215
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Term
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Definition
HNMR-->carboxyl Hs at 10-13
CNMR-->carboxyl Cs at 160-180 |
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Term
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Definition
| HNMR-->.5-5.0; not very distinctive |
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Term
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Definition
1. look at molecular formula: determine SODAR
2. # of signals: to determine # of diff. types of H/C
3. Integration: to determine # of Hs in each signal
4. Pattern of chemical shift: to determine functional groups
5. Splitting patterns: to determine # of nearest nonequivalent Hs
6. Structural formula: make possible structures from previous info and confirm by checking w/ spectra |
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