Separation Techniques and spectroscopy

Question 1

What kind of technique is mass spectrometry ? What is it used for?

Answer 1

IDENTIFICATION Technique
Mass spectrometry is a very SPECIFIC technique, which can be used to determine the mass of compounds in a sample.
It is specific enough to identify amino acids and proteins

Question 2

when are organic molecules more water soluble ?

Answer 2

when they are CHARGED

Question 3

What components are required for solvent extractions?

Answer 3

Solvent extractions require two solvents that are not soluble in each other (ex: diethyl ether and water)

Question 4

What functional group has an IR peak of 3200-3500 ?

Answer 4

OH bonds

Question 5

which functional group has an IR peak of about 1700 ?

Answer 5

ketones (C=O )

Question 6

which functional group has a peak about 2900?

Answer 6

C–H bond

Question 7

During extractions, what is NaHCo3 used for?

Answer 7

only to DEPROTONATE Carboxlic acids (COOH —> COO- )

Question 8

During extractions what is NaOH used for?

Answer 8

to Deprotonate PHENOLS and Carboxylic acids

Question 9

During extractions what is HCL used for?

Answer 9

to PROTONATE AMINES (R3N —> R3NH+ Cl- )

Question 10

What is distillation used for? What does it distinguish ?

Answer 10

Distillation used to separate liquids. it used separate low boiling point compounds

Question 11

What is column chromatography used for? What property does it exploit? What is elution order?

Answer 11

used to separate molecules based on POLARITY . it separates large amounts of high molecular weight compounds
-elution order: non polar molecules first, polar last

Question 12

what does toluene describe for organic molecules ?

Answer 12

Toluene is a COMMON name (NOT IUPAC)

Question 13

Describe relationship between volatility and intermolecular forces? How does this affect elution ?

Answer 13

In general, molecules with stronger intermolecular forces are LESS volatile

-greater volatility (weaker IMF), faster elution

Question 14

How do you analyze an enantiomeric ratio of a compound?

Answer 14

enantiomers must be treated with a reagent with known stereochemistry, called a chiral resolving reagent, to create diastereomers which can be separated.

(then analyze using gas chromatography)

Question 15

Describe splitting pattern in HNMR

Answer 15

The number of peaks in the splitting pattern is n + 1, where n is the number of protons on the neighboring carbon.

Question 16

what is order of increasing acidity for ester, alcohol and carboxylic acid?

Answer 16

Ester < alcohol< carboxylic acid
(carboxylic acid is most acidic )

Question 17

When does distillation not work for compounds ?

Answer 17

when compounds are SOLID (or too large)

Question 18

What is a bronstead Lowry acid ?

Answer 18

Bronstead Lowry acid: donates H+ (protons)

Question 19

What does alcohol stretch on IR look like?

Answer 19

broad peak around 3200-3600 cm–1.

Question 20

what does alkyne (triple bond) stretch appear on IR ?

Answer 20

peak around 2100-2600 cm–1 range

Question 21

what is C-H bond stretch in IR>

Answer 21

C—H stretch is near 2950 cm–1.

Question 22

What does a chemical shift of 4.3 ppm imply?

Answer 22

A chemical shift of 4.3 ppm represents a hydrogen next to a highly electronegative atom
ex: hydrogen next to the O in the ester bond.

Question 23

When is HPLC (high performance liquid chromatography) used ?

Answer 23

HPLC can be used to separate the compounds on the basis of their different polarities.

Question 24

When can extraction be used in an experiment ?

Answer 24

Extraction is only useful if one of the compounds in a mixture is more SOLUBLE in an aqueous layer compared to the other, meaning one compound contains an amine, a carboxylic acid, or a phenol while the other does not. I

Question 25

How do you identify a compound to be racemic ?

Answer 25

if a compound has ONE STEREOCENTER , it will be a racemic mixture (mix of enantiomers)

Question 26

What do enantiomers have in common? How does this affect separation techniques

Answer 26

enantiomers have the same solubility, boiling point, and polarity

hence Extraction (solubility) , Distillation (boiling point) and Chromatography (polarity) (extraction), cannot be separation techniques used for enantiomers.