IM Forces and Lab Techniques

Question 1

Is cyclohexane a polar or nonpolar?

Answer 1

Nonpolar

Question 2

Is toluene a polar or nonpolar solvent?

Answer 2

Nonpolar solvent

Question 3

Fingerprint region

Answer 3

The 600-1400 cm^-1 region found exclusively within IR spectrums and is unique to each molecule

Question 4

silica gel chromatography separates compounds based on __________

Answer 4

Polarity

Question 5

What compounds elute first/last in silica gel chromatography

Answer 5

Silica gel has a polar surface so it interacts more with polar molecules, thus polar molecules stick to the column and take longer to elute (elute last) and nonpolar molecules elute first

Question 6

what is infared (IR) spectroscopy used for?

Answer 6

• to identfy the functional group present in a molecule

Question 7

what is nuclear magnetic resonance (NMR) spectroscopy used for?

Answer 7

• tool used to determine the molecular structure of a compound
• 2 types: HNMR and CNMR

Question 8

chemical shift of HNMR signals:

Answer 8

• a proton with less electron density around it is considered to be deshielded (protons next to EN atoms, EN atom withdraws electron density) –> appears further to the left (downfield)
• a proton with more electron density around it is considered shielded (further from EN atom) –> appears to the right (upfield)

Question 9

HNMR signal for alcohol and amines H’s

Answer 9

~ 0.5/1 - 5/5.5

Question 10

HNMR signal for aromatic ring H’s

Answer 10

~ 6-8

Question 11

HNMR signal for aldehyde H

Answer 11

~ 9 - 10

Question 12

HNMR signal for sp3 hybridized carbon H’s

Answer 12

~ 0.5 - 3.5

Question 13

HNMR signal for phenol (PhOH) H

Answer 13

~ 4 - 8

Question 14

HNMR signal for sp2 hybridized carbon H’s (doubl bond)

Answer 14

~ 4 - 6

Question 15

HNMR signal for amide’s H (RCONH)

Answer 15

~ 5.5 - 9.5

Question 16

HNMR signal for carboxylic acid H’s

Answer 16

~ 11- 14

Question 17

what apparatus is used for liquid-liquid extractions?

Answer 17

separatory funnel

Question 18

what is recrystallization used for?

Answer 18

• a method to purify solids
• if a chemical reaction results in a solid precipitate, the solid most likely containes impurities because impurities get trapped in the solid lattice as it forms

Question 19

what form of distillation is used for 2 liquids whose boiling point differs by at least 50°C?

Answer 19

simple distillation

Question 20

what form of distillation is used for 2 liquids whose boiling point differs by 25°C or less?

Answer 20

fractional distilation