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Organic Chemistry DAT > Spectroscopy > Flashcards

Spectroscopy Flashcards

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1
Q

Absorption

A

Electron is excited to a high-energy orbital (HOMO to LUMO)

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2
Q

Emission

A

Electron relaxes back to a lower-energy orbital (LUMO to HOMO)

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3
Q

UV-Vis Spec is good to visualize _____?

A

Pi Electrons. Will promote an electron on a pi-bonding orbital to a pi antibonding orbital.

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4
Q

Spectroscopy

A

The interaction between light and matter

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5
Q

IR Spectroscopy induces _?

A

Symmetric and asymmetric stretching and bending of bonds

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6
Q

What bond is seen at 2840-3000cm^-1?

A

saturated C-H on alkane

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7
Q

What bond is seen at 3200-3650cm^-1

A

broad and rounded O-H stretch

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8
Q

What bond is seen at 1630-1780 cm^-1

A

C=O stretch (narrow and pointed)

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9
Q

On IR Spectrum, what does the x-axis and y-axis display?

A

X-axis - wavenumber
Y-axis - transmittance

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10
Q

In HNMR looks at?

A

Chemical shift
Integration
Splitting Patterns

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11
Q

What is the reference peak on NMR spetra?

A

Tetramethylsilane (TMS) at 0 ppm.

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12
Q

What happens if a proton is close to an electronegative atom?

A

It will have its electron density withdrawn or deshielded. Peak will be futher downfield (to the left)

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13
Q

Integration values

A

Relative to a reference peak
The higher the peak, the more chemically equivalent protons.

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14
Q

When evaluating splitting patterns

A

Neighboring protons will create singlets, doublets, and so on. Each resonance is split into (n +1) peaks n = # of neighboring protons.

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15
Q

Shifts for benzene rings in HNMR

A

Will be jumbled together usually seen between 7-8ppm.

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16
Q

How do you calculate degrees of unsaturation in hydrocarbons?

A

(max #H atoms - actual # H atoms)/2
fully saturated hydrocarbons: CnH2n+2

17
Q

How to calculate the degrees of unsaturation in molecules with heteroatoms

A

DOF = (2C + 2 + N - X - H)/2

18
Q

Value for hydroxyl/amino protons in HNMR?

A

0.5-5.5ppm

19
Q

Value for sp3 C protons in HNMR?

A

1-5ppm

20
Q

Value for sp2 C protons in HNMR?

A

4-6ppm

21
Q

Value for aromatic protons in HNMR?

A

6-8ppm (identifies 4 DOF)

22
Q

Value for aldehyde/phenol protons in HNMR?

A

~10ppm

23
Q

Value for carboxyl/amide protons in HNMR?

A

12-14ppm

24
Q

Value for esters/amides/carboxylic acid carbons in 13CNMR?

A

160-180 ppm

25
Q

Value for aldehydes/ketone carbons in 13CNMR?

A

200-280ppm

26
Q

Value for sp3 alkane carbons in 13CNMR?

A

10-50ppm

27
Q

Value for sp2 alkene carbons in 13CNMR?

A

100-155ppm

28
Q

Value for aromatic carbons in 13CNMR?

A

120-180ppm

29
Q

Chromatography separates substances on the basis of differing:

A

Polarity

30
Q

The (blank) polar a substance, the more (blank) it will travel up a TLC plate.

A

More; Slowly

31
Q

Rf value must be between what values?

A

0;1

32
Q

Extraction separates liquids on the basis of differing:

A

Solubility

33
Q

Which substance would be most useful in separating benzoic acid and napththalene?

A

acqueous base like NaHCO3

34
Q

In Gas Chromatograhy, what factors cause a lower retention time?

A

Lower BP
Lower solubility
Hotter column

35
Q

Distillation separates liquids on a basis differing in:

A

Boiling points

36
Q

After recrystallization, melting point analysis can be performed. How do you know you have a pure substance based on melting values?

A

Narrow range clsoe to tabulated value.

37
Q

What kind of solvent is ideal for recrystallization?

A

Low solubility at room temperature and high solubility at high temperatures. Impurity should have high solubility at room temperature or insolubility at high temperature to remove while boiling

38
Q

What is Tollen’s test?

A

Mainly used to test for aldehydes. In the reaction, silver ammonia complex ions react with aldehydes to form solid silver and carboxylate ions. The indicator of a positive result is a silver layer along the inside of the test tube.

39
Q
A

Organic Chemistry DAT (1 decks)

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