Separations and Purifications . *** Flashcards

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1
Q

extraction

A

combines two immiscible liquids, one of which easily dissolves the compound of interest.

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2
Q

Polar (water) layer is called the

A

aqueous phase and dissolves compounds with hydrogen bonding or polarity.

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3
Q

Organic phase

A

nonpolar layer and dissolves nonpolar compounds.

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4
Q

Extraction is carried out in a

A

separatory funnel. One phase is collected and the solvent is then evaporated.

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5
Q

acid-base properties can be used to

A

can be used to increase solubility .

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6
Q

wash

A

is the reverse of extraction, in which small amounts of solute that dissolves impurities is run over the compound of interest.

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7
Q

Filtration

A

isolates a solid (residue) from a liquid (filtrate).

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8
Q

gravity filtration

A

is used when the product of interest is in the filtrate. Hot solvent is used to maintain solubility.

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9
Q

Vacuum filtration

A

is used when the product of interest is the solid. A vacuum is used when the product of interest is the solid. A vacuum is connected out the flask to pull the solvent through more quickly.

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10
Q

Recrystallization

A

the product is dissolved in a minimum amount of hot solvent. If the impurities are more soluble, the crystals will reform while the flask cools, excluding the impurities.

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11
Q

Distillation

A

separates liquids according to differences in their boiling points; the liquid with the lowest boiling point vaporizes first and is collected as distillate.

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12
Q

Simple distillation

A

can be used if the boiling points are under 150 C and are at least 25 C apart.

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13
Q

Vacuum distillation

A

should be used if the boiling points are over 150 C to prevent degradation of the product.

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14
Q

Fractional distillation

A

should be used if the boiling points are less than 25 C apart because it allows more refined separation of liquids by boiling points.

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15
Q

Chromatography

A

use two phases to separate compounds base on physical or chemical properties.

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16
Q

Stationary phase or adsorbent

A

is usually a polar solid .

17
Q

Mobile phase

A

runs through the stationary phase and is usually a liquid or gas. This elutes the sample through the stationary phase.

18
Q

Compounds with higher affinity for the stationary phase have smaller

A

retardation factors and take longer to pass through, if at all; compounds with higher affinity for the mobile phase elute through more quickly. Compounds therefore get separated form each other, called partitioning.

19
Q

Thin layer and paper chromatography

A

are used to identify a sample:
-stationary phase is polar material, such as silica, alumina, or paper.
-mobile phase is a nonpolar solvent, which climbs the card through capillary action.
-the card is spotted and developed; Rf values can be calculated and compared to reference values.
reverse-phase chromatography uses a nonpolar card with a polar solvent.

20
Q

column chromatography

A

utilizes polarity, size or affinity to separate compounds based on their physical or chemical properties.

  • stationary phase is column containing silica or alumina beads.
  • mobile phase is a a nonpolar solvent, which travels through the column by gravity.
21
Q

Ion-exchange chromatography

A

beads are coated with charged substances to bind to compounds with opposite charge.

22
Q

size-exclusion chromatography .

A

beads have small pores which trap smaller compounds and allow larger compounds to travel through faster.

23
Q

affinity chromatography

A

the column is made to have high affinity for a compound by coating the beads with a receptor or antibody to the compound.

24
Q

Gas chromatography

A

separates vaporizable compounds according to how well they adhere to the adsorbent in the column.

  • stationary phase is a coil of crushed metal or a polymer
  • the mobile phase is a nonreactive gas
  • gas chromatography may be convinced in sequence with mass spectrometry, which ionizes and fragments molecules and passes these fragments through a magnetic field to determine molecular weight or structure.
25
Q

High-performance liquid chromatography (HPLC)

A

is similar to column chromatography but uses sophisticated computer-mediated solvent and temperature gradients. It is used if the sample size is small or if forces as capillary action will affect results. It was formerly called high-pressure liquid chromatography.

26
Q

retardation factor

A

Rf = distance spot moved/distance solvent front moved

27
Q

Extraction depends on what three intermolecular force

A
  1. hydrogen bonding: like alcohols, acids, will move to aq layer
  2. dipole-dipole interactions: these are less likely to move to aq
  3. vander waals: with only these, compounds are least likely move to the aq