CHM2211L UF Exam #1 Questions with correct answers
Melting Point - ✔✔temperature at which the solid phase is in equilibrium with the
liquid phase
Pure Compound - ✔✔sharp melting point, range is narrow (1-2 degrees)
Why does the presence of a soluble impurity in a sample has the effect of
lowering and broadening the melting point range? - ✔✔because the impurity
disrupts the crystalline lattice of the sample so less energy is required to convert
the solid phase into a liquid phase
What effects does insoluble impurity like sand and glass has on MP? - ✔✔no
effect
Errors of taking melting points: - ✔✔1. improper amount of sample in capillary
tube 2) mistaking sagging or shrinking sample as melting 3) presence of solvent
cause crystals to "sweat"
Benzoic acid - ✔✔122-123°C
Mandelic acid - ✔✔120-122°C
An unknown compound was determined to be 74.97% C, 8.39% H, and no
nitrogen. What is the empirical formula - ✔✔100-74.97-8.39 = 16.64% O
# of C: 74.97/12 = 6.25/1.04 = 6
# of H: 8.39/1=8.39/1.04= 8
,# of O: 16.64/16 = 1.04/1.04 = 1
EmF: C6H8O
Can IR spectroscopy be used to distinguish 2-pentanone from 2-hexanone? why
or why not? - ✔✔No because IR spectroscopy is used to distinguish functional
groups presents on molecules. Both 2-p and 2-h contains the same functional
group.
Acetophenetidin - ✔✔analgesic and antipyretic (pain and fever relief)
p-acetamidophenol - ✔✔Williamson ether synthesis
p-phenetidine - ✔✔Amide synthesis
Recrystallization - ✔✔solvent that will completely dissolve both desired
compound and impurities when the solvent is hot; desire compound must be
insoluble in the chosen solved at cold temperature and inorganic remains soluble
when cooled
What do seed crystals do? - ✔✔They serve as nucleation sites where more
molecules of the desired compound deposit themselves in layers.
Explain the purpose of the hot gravity filtration. Why is it good to use the stemless
funnel for this technique? - ✔✔- Hot gravity filtration serves to remove any
insoluble impurities that do not dissolve when the solution is brought to its
boiling point.
, - it is good to use the stemless funnel for this technique because this would
minimize any contact between the hot solution and the funnel. If a funnel with
stem is used the droplets of hot solution might get stuck on the stem inner
surface and early crystallization of the solution might occur
ligroin - ✔✔solvent derived from petroleum consisting of C7 and C8 hydrocarbon,
non polar
Amide synthesis of acetophenetidin - ✔✔p-phenetidine + acetic anhydride
(solvent: Sodium acetate and hydrochloric acid)
Why is the sample of p-phenetidine reddish brown? - ✔✔small amount of
impurities caused by air oxidation of the amino functional group
how to remove reddish brown from p-phenetidine? - ✔✔decolorizing carbon
Why should you not stir the crystals in the buchner funner? - ✔✔this makes the
filtration less efficient and does not adequately remove the solvent from the
crystal
Williamson Ether Synthesis - ✔✔1) p-acetamidophenol +sodium methoxide,
methanol, and ethanol
2) 1st product (addition of sodium) + Bromoethane
Why does the williamson ether synthesis take two steps? - ✔✔Because the
hydrogen on the alcohol group of acetamidophenol would react with the
bromoethane to create ethane and there would not be any reaction. The sodium
Melting Point - ✔✔temperature at which the solid phase is in equilibrium with the
liquid phase
Pure Compound - ✔✔sharp melting point, range is narrow (1-2 degrees)
Why does the presence of a soluble impurity in a sample has the effect of
lowering and broadening the melting point range? - ✔✔because the impurity
disrupts the crystalline lattice of the sample so less energy is required to convert
the solid phase into a liquid phase
What effects does insoluble impurity like sand and glass has on MP? - ✔✔no
effect
Errors of taking melting points: - ✔✔1. improper amount of sample in capillary
tube 2) mistaking sagging or shrinking sample as melting 3) presence of solvent
cause crystals to "sweat"
Benzoic acid - ✔✔122-123°C
Mandelic acid - ✔✔120-122°C
An unknown compound was determined to be 74.97% C, 8.39% H, and no
nitrogen. What is the empirical formula - ✔✔100-74.97-8.39 = 16.64% O
# of C: 74.97/12 = 6.25/1.04 = 6
# of H: 8.39/1=8.39/1.04= 8
,# of O: 16.64/16 = 1.04/1.04 = 1
EmF: C6H8O
Can IR spectroscopy be used to distinguish 2-pentanone from 2-hexanone? why
or why not? - ✔✔No because IR spectroscopy is used to distinguish functional
groups presents on molecules. Both 2-p and 2-h contains the same functional
group.
Acetophenetidin - ✔✔analgesic and antipyretic (pain and fever relief)
p-acetamidophenol - ✔✔Williamson ether synthesis
p-phenetidine - ✔✔Amide synthesis
Recrystallization - ✔✔solvent that will completely dissolve both desired
compound and impurities when the solvent is hot; desire compound must be
insoluble in the chosen solved at cold temperature and inorganic remains soluble
when cooled
What do seed crystals do? - ✔✔They serve as nucleation sites where more
molecules of the desired compound deposit themselves in layers.
Explain the purpose of the hot gravity filtration. Why is it good to use the stemless
funnel for this technique? - ✔✔- Hot gravity filtration serves to remove any
insoluble impurities that do not dissolve when the solution is brought to its
boiling point.
, - it is good to use the stemless funnel for this technique because this would
minimize any contact between the hot solution and the funnel. If a funnel with
stem is used the droplets of hot solution might get stuck on the stem inner
surface and early crystallization of the solution might occur
ligroin - ✔✔solvent derived from petroleum consisting of C7 and C8 hydrocarbon,
non polar
Amide synthesis of acetophenetidin - ✔✔p-phenetidine + acetic anhydride
(solvent: Sodium acetate and hydrochloric acid)
Why is the sample of p-phenetidine reddish brown? - ✔✔small amount of
impurities caused by air oxidation of the amino functional group
how to remove reddish brown from p-phenetidine? - ✔✔decolorizing carbon
Why should you not stir the crystals in the buchner funner? - ✔✔this makes the
filtration less efficient and does not adequately remove the solvent from the
crystal
Williamson Ether Synthesis - ✔✔1) p-acetamidophenol +sodium methoxide,
methanol, and ethanol
2) 1st product (addition of sodium) + Bromoethane
Why does the williamson ether synthesis take two steps? - ✔✔Because the
hydrogen on the alcohol group of acetamidophenol would react with the
bromoethane to create ethane and there would not be any reaction. The sodium
