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Spectroscopy ranges Flashcards

1
Q

NMR Spetroscopy

A

Obtain information on chemical & structural environment of nuclei

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2
Q

IR Spectroscopy

A

Information about types of bonds present

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3
Q

Mass Spectrometry

A

Technique effectively weighs molecules

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4
Q

UV/Vis Spectroscopy

A

Gives a characteristic absorption spectrum

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5
Q

X-Ray Crystallography

A

Determines the position of atoms within a crystal

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6
Q

Elemental analysis

A

Percentage-by-mass of elements in a compound determined

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7
Q

HNMR 0-3ppm

A

Protons bonded to sp3 C without electronegative

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8
Q

HNMR 3-5ppm

A

Protons bonded to sp3 C with electronegative

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9
Q

HNMR 5-10ppm

A

Protons bonded to sp2 C (double bonds & aromatic)

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10
Q

HNMR Coupling and Integration

A

Coupling present (usually seen over 3 bonds), Integration possible as area proportional to protons responsible

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11
Q

HNMR Solvents

A

Deuterochloroform (CDCl3) = 7.26ppm

Deuteromethanol (CD3OD) = 3.35ppm (quintet), 4.8ppm

d6-Dimethyl sulphoxide (d6-DMSO, (CD3)2SO) = 2.50ppm (quintet)

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12
Q

HNMR Amine RNH2 or R2NH

A

0.5 -4.5ppm

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13
Q

HNMR Aromatic amines ArNH2 or ArNHR

A

3-6ppm

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14
Q

HNMR Amides RCONH2 or RCONHR

A

5-12ppm

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15
Q

HNMR Alcohols ROH

A

0.5 - 4.5ppm

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16
Q

HNMR Phenols ArOH

A

4.5 - 10ppm

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17
Q

HNMR Carboxylic acids RCOOH

A

9-15ppm

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18
Q

HNMR How to improve OH & NH peaks

A

Peaks very broad and coupling not usually seen due to proton exchange
If rate slowed down, OH & NH signals become sharper & couplings seen -> achieved using d6-DMSO as solvent or making very dilute sample

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19
Q

13CNMR 0-50ppm

A

sp3 C without electronegative

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20
Q

13CNMR 50-100ppm

A

sp3 C with electronegative

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21
Q

13CNMR 100-150ppm

A

sp2 C (double bonds & aromatic) without electronegative

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22
Q

13CNMR 150-200ppm

A

sp2 C with electronegative

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23
Q

13CNMR Carbonyl Acids/Amides

A

160-175ppm

24
Q

13CNMR Aldehyde & Ketones

A

~200ppm, Ketones typically just over, Aldehydes typically just under

25
Q

13CNMR C=N

A

Usually in 150-200ppm range but can be as low as 120ppm

26
Q

13CNMR Electronegative substituents

A

Oxygen = +50ppm
Chlorine = +30ppm
Alkyl = +9ppm
Phenyl ring/C=C = +20ppm

27
Q

13CNMR Coupling and Integration

A

Coupling usually not taken into account as 13C spectra proton decoupled & Integration can’t be used as size of peak may be qualitative indicator but not always the case e.g. quaternary C resonances usually weaker as no protons attached to make it relax faster

28
Q

13CNMR Solvents

A

Deuterochloroform (CDCl3) = 77.0 ppm (1:1:1 triplet)

Deuteromethanol (CD3OD) = 49.1 ppm (septet)

d6-Dimethyl sulphoxide (d6-DMSO, (CD3)2SO) = 39.6ppm (septet)

29
Q

IR four regions

A

2500 - 4000cm^-1 = Vibrations of X-H
2000 - 2500cm^-1 = Vibrations of Triple bonds
1500 - 1900cm^-1 = Vibrations of Double bonds
<1500cm^-1 = Fingerprint region

30
Q

IR C-H

A

2900-3200cm^-1 (sharp but usually multiple so peak spread out)

31
Q

IR O-H

A

3500-3600cm^-1 (sharp, if not involved in H bonding)

2900-3500cm^-1 (broad, if involved in H bonding)

32
Q

IR N-H

A

~3300cm^-1 (sharp)

33
Q

IR NH2

A

~3300cm^-1 (sym) & ~3400cm^-1 (asym) [sharp,strong]

34
Q

IR R-CN

A

2220 -2260cm^-1

35
Q

IR R-CC-H

A

2100-2140cm^-1

36
Q

IR R-CC-R’

A

~2200cm^-1 (weak)

37
Q

IR RCOCl (acid chloride)

A

1750-1815cm^-1 (sharp & strong)

38
Q

IR RC(O)OC(O)R (acid anhydride)

A

1740-1790cm^-1 (asym) & 1800-1850cm^-1 (sym) [sharp & strong]

39
Q

IR ROC(O)OR (carbonates)

A

1740-1780cm^-1 (sharp & strong)

40
Q

IR RCOOR (ester)

A

1735-1750cm^-1 (sharp & strong)

41
Q

IR RC(O)H (aldehyde)

A

1730cm^-1 (sharp & strong)

42
Q

IR R2C=O (ketone)

A

1715cm^-1 (sharp & strong)

43
Q

IR RCOOH (carboxylic acid)

A

1700-1740cm^-1 (sharp & strong)

44
Q

IR RCONR2 (amide)

A

1640-1690cm^-1 (sharp & strong)

45
Q

IR RCO2- (carboxylate anion)

A

1300-1420cm^-1 & 1550-1610cm^-1 (sharp & strong)

46
Q

IR C=C

A

~1640cm^-1 (weak)

47
Q

IR Benzene rings

A

1500-1600cm^-1 (2 or 3 sharp absorptions)

48
Q

IR NO2 (nitro groups)

A

1350cm^-1 (sym) and 1530cm^-1 (asym)

49
Q

IR Fingerprint region

A

many kind of bond vibrations found here, highly specific for each individual compound. Peaks not usually selected from here to individually assign

50
Q

Mass Spectra ionisation technique

A

electrospray = (M+H)+

electron impact = M+

51
Q

CNMR Alkyne (sp C)

52
Q

IR Vibrating Diatomic formula

A

f = ((2[pi]c)^-1)(k/μ)^0.5 where μ = m1m2/(m1+m2)

53
Q

IR Absorption criterion

A

If no change in the dipole moment when the bond stretches then it will not absorb IR at all

54
Q

IR Carbonyl strengthening/weakening

A

Anything that strengthens C=O give rise to absorption at higher freq ->strengthened by electron withdrawing
Anything that weakens C=O give rise to absorption at lower freq -> weakened by electron donating

55
Q

IR Conjugation

A

Lowers base frequency by 20-30cm^-1

56
Q

IR ring structure

A

smaller the ring size, higher the stretching frequency -> doesn’t alter strength of bond significantly but increases resistance via repulsion

Chemistry (2 decks)

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