Part 5

Question 1

TMS

Answer 1

provides a reference peak. The signal for its H atoms is assigned a delta = 0.

Question 2

Downfield

Answer 2

Deshielded

Question 3

Carbon NMR

Answer 3

Can show:

1. The number of different carbons with their relative chemical environments.
2. Their number of hydrogens (spin coupled NMR only)

Question 4

UV Spectroscopy

Answer 4

Most useful for studying compounds containing double bonds, and/or hetero atoms with lone pairs.

Can be applied quantitatively by using Beer’s law.

Question 5

Beer’s law

Answer 5

A = epsilon(b)(c)

A = absorbance (measured by UV)
(epsilon) = a constant for the substance at a given wavelenght.
b = path length (usually equal to one)
c = concentration

Question 6

Mass Spectrometry

Answer 6

Differs in that it is not true spectroscopy.

No absorption of electromagnetic radiation is involved.

Does not allow for reuse of sample.

Helps in distinguishing certain compounds.

Question 7

Extraction

Answer 7

Separates dissolved substances based on differential solubility in aqueous versus organic solvents (oil and water).

hydrogen bonding: alcohols/acids –> aqueous

dipole-dipole: less likely to move to aqueous

van der Waals: compounds are least likely to move into aqueous layer.

Question 8

Filtration

Answer 8

Separates solids from liquids

Question 9

Recrystallization

Answer 9

Separates solids based on differential solubility; temperature is important here.

Question 10

Sublimation

Answer 10

Separates solids based on their ability to sublime.

Must raise the temp at a low enough pressure, or lower the pressure at a very cold temperature.

Question 11

Centrifugation

Answer 11

Separates large things (like cells, organelles, and macromolecules) based on mass and density.

Question 12

Distillation

Answer 12

Separates liquids based on boiling point, which in turn depends on intermolecular forces.

Question 13

Chromatography

Answer 13

Uses a stationary phase and a mobile phase to separate compounds based on how tightly they adhere (generally due to polarity but sometimes size as well).

Question 14

Electrophoresis

Answer 14

Used to separate biological macromolecules (such as proteins or nucleic acids) based on size and sometimes charge.

Question 15

Amines

Answer 15

Boiling points of amines are between those of alkanes and alcohols.

Are bases and readily accept protons to form ammonium ions.

Function as weak acids.

Question 16

Alkylation of Ammonia (Direct)

Answer 16

Alkyl halides + ammonia (NH3) –> alkylammonium halide salts.

Ammonia functions as a nucleophile and displaces the halide atom. When the salt is treated with a base, the alkylamine product is formed.

A SN2 reaction: halides are good leaving groups and ammonia is a good nucleophile

Question 17

Gabriel synthesis

Answer 17

Converts a primary alkyl halide to a primary amine.

Also a SN2 reaction.

Question 18

Amines can be formed by:

Answer 18

1. SN2 reactions: ammonia reacting with alkyl halides or gabriel synthesis.
2. Reduction of: amides, aniline and its derivatives, nitriles, and imines.

Amines can be destroyed (converted to alkenes) by exhaustive methylation.

Question 19

Nitro Compounds + (Fe or Zn) + diluted HCl –> ?

Answer 19

Product: Nitro replaced with Amine.

Useful for aromatic compounds, because nitration of aromatic rings is facile.

Fe or Zn + HCl: common reducing agent.

Question 20

Nitriles + (Hydrogen/catalyst or with LAH) –> ?

Answer 20

Product: Primary amines