CHM205 Orgo Lab Final

PIPETS/MP: What is the proper heating rate used to determine a compounds melting point range?

1-2 degrees per minute

PIPETS/MP: You're determining the melting point of a compound, and it turns from white to brown before melting. What has happened here?

Decomposition

PIPETS/MP: You're determining the melting point of a compound, and it slowly disappears from the capillary tube before melting. What has happened here?

Sublimation

RECRYSTALLIZATION: What is a major safety concern of using acetone as a recrystallization solvent?

Flammable

RECRYSTALLIZATION: What would happen to the solution if you didn't use a pre-heated filter during the "hot" gravity filtration step?

Crystals form in the filter paper

RECRYSTALLIZATION: Why is benzyl alcohol a poor choice of solvent? (BP 205ºC, fluorenol with MP of 153º-155º)

Boiling point too high, solution will not be saturated enough

RECRYSTALLIZATION: What kind of contaminant is removed by the addition of charcoal before filtration?

Colored organic contaminant

RECRYSTALLIZATION: What kind of contaminant is removed with just hot gravity filtration?

Inorganic (sand)

RECRYSTALLIZATION: What kind of contaminant would remain dissolved in the solvent and not form in the crystal?

Very soluble contaminant

RECRYSTALLIZATION: What would be the effect of using too much solvent while dissolving a solid for recrystallization?

Crystals would stay dissolved instead of recrystallizing

RECRYSTALLIZATION: The solubility of compound X in ethanol is found to be 0.21g per 10 mL at 0ºC, and 1.4g per 10 mL at 78ºC. What is the minimum amount of ethanol needed to recrystallize a 2.0g sample of compound X? How much of compound X will remain in the cold solvent?

14.3 mL

RECRYSTALLIZATION: Why use an Erlenmeyer flask?

Reduces evaporation

RECRYSTALLIZATION: What is the purpose of the activated charcoal?

Removes colored impurities

RECRYSTALLIZATION: Where does the color come from in purities?

Chromophores

RECRYSTALLIZATION: Why use fluted filter paper? (2 reasons)

Increase surface area, increase rate of filtration

RECRYSTALLIZATION: What apparatus is used for a micro-scale recrystallization?

Craig tube in centrifuge tube

RECRYSTALLIZATION: What type of filtration is used for macro-scale recrystallization?

Vacuum

RECRYSTALLIZATION: How does solubility relate to temperature?

Temperature increases, solubility increases

RECRYSTALLIZATION: How should filtrate be cooled in order to form the most pure crystals?

SLOWLY

EXTRACTION: RCO2H + NaOH --> ?

RCO2-Na+ + H2O

EXTRACTION: ArOH + NaOH --> ?

ArO-Na+ + H2O

EXTRACTION: RCO2H + NaHCO3 (aq) --> ?

RCO2-Na+ + H2O

EXTRACTION: ArOH + NaHCO3 (aq) --> ?

no reaction (NR)

EXTRACTION: RNH2 + HCl (aq) --> ?

RNH3+Cl- (aq)

EXTRACTION: What is the ratio of concentration of a solute in each layer called?

Partition coefficient

EXTRACTION: What is the formula for the partition coefficient (K)?

K = C2/C1

EXTRACTION: What is used to remove leftover water form isolated compound in organic solvent?

Drying agent

EXTRACTION: What are commonly used as drying agents?

Anhydrous salts

EXTRACTION: Go memorize your flow chart until you can recreate it from scratch. Once you've done that, answer "Yes" to this question. Done?

Yes

EXTRACTION: What is the purpose of back extraction?

Ensures no organic solvent was transferred over with aqueous solution, vice-versa

CHROMATOGRAPHY: TLC is a _______/_______ chromatography

solid; liquid

CHROMATOGRAPHY: What serves as the stationary phase in TLC?

Silica gel plate

CHROMATOGRAPHY: What serves as the mobile phase in TLC?

Liquid solvent

CHROMATOGRAPHY: Because of the polarity of the plate, will a more polar compound or a less polar compound travel up the plate faster?

Less polar compound

CHROMATOGRAPHY: Why does a more polar compound elute after a less polar one from the column?

It has stronger intermolecular forces with the stationary phase

CHROMATOGRAPHY: What two mediums are used to visualize clear compounds on a TLC plate?

UV light; iodine

CHROMATOGRAPHY: What is the retardation factor (Rf)?

Ratio of how far the compound travels in relation to the solvent

CHROMATOGRAPHY: Which will have a higher Rf value--more polar or less polar compound?

Less polar compound

CHROMATOGRAPHY: How is Rf calculated?

Distance travelled by compound / distance travelled by solvent front

CHROMATOGRAPHY: What is the purpose of the wick when running TLC?

Saturates air inside jar with solvent

CHROMATOGRAPHY: What is it called when small columns are filled with dry adsorbent, then fluent is added to saturate the column?

Dry packing

CHROMATOGRAPHY: What is it called when adsorbent and solvent are mixed in beaker to form a slurry, which is then poured in and excess solvent drains?

Wet packing

CHROMATOGRAPHY: List the following organic solvents in order from least polar to most polar: ethyl acetate, water, dichloromethane, n-propanol, ethanol, toluene, heptane

Heptane, toluene, dichloromethane, ethyl acetate, n-propanol, ethanol, water

POLYMERS: In what type of polymerization reaction is a small molecule, like HCl or H2O, lost while two monomers form a larger unit?

Condensation

POLYMERS: Polyamides and polyesters are classic examples of what kind of polymerization reaction?

Condensation

POLYMERS: What kind of polymerization reaction uses an initiator to form a reactive species?

Chain addition polymerization

POLYMERS: Polystyrene is generated from which type of polymerization reaction?

Chain addition polymerization

POLYMERS: "Slime" made from PVA and borax, is what type of polymer?

Cross-linked polymer

POLYMERS: Chain addition polymers have what kind of backbone?

Hydrocarbon

POLYMERS: Condensation polymers have what as part of the polymer backbone?

Functional groups

DISTILLATION: Equation to calculate correction factor for T?

C=At/At

DISTILLATION: Equation to calculate correction factor for C?

Cc=Ac/At

DISTILLATION: Equation to calculate corrected area for C?

CA=Ac/Cc

DISTILLATION: Equation to calculate corrected area for T?

CA=At (because correction factor is 1)

DISTILLATION: Equation to calculate volume percent?

V%=CA/(CAc+CAt) * 100%

DISTILLATION: What occurs when the sum of the partial pressures equals atmospheric pressures?

Boiling

DISTILLATION: What kind of distillation is used to purify compounds that are already pure, have very small amounts of non-volatile impurities, or if the compound and impurities have very different boiling points?

Simple distillation

DISTILLATION: What kind of distillation is the performance of several simple distillations over and over in one step?

Fractional distillation

DISTILLATION: What kind of distillation do you use when the substances are miscible with similar boiling points?

Fractional distillation

DISTILLATION: What kind of distillation do you use when you have a nearly pure substance or substances with at least 100º difference in boiling point?

Simple distillation

DISTILLATION: What kind of distillation do you use when you have immiscible compounds, or compounds with very high boiling points?

Steam distillation

DISTILLATION: Why does steam distillation work for compounds with high boiling points?

System boils at lower boiling point than either compound

DISTILLATION: What are the stationary and mobile phases in gas chromatography, respectively?

liquid; carrier gas

DISTILLATION: Which compound passes through gas chromatography faster, and why?

Lower bp; higher vapor pressure

EXTRACTION: Traumatic acid has a distribution coefficient of 5.8 between MtBE and water. If 75 mg of traumatic acid is added to a centrifuge tube containing 3mL of water and 2mL of MtBE, how much traumatic acid would be in each layer after mixing?

59.59 MtBE, 15.41 aqueous

EXTRACTION: What should you do if you notice there are still tiny water droplets in the organic layer just before adding a drying agent?

Remove them with a pipet before proceeding

CHROMATOGRAPHY: Why does ortho-hydroxyacetophenone have such a lower boiling point than para-?

Intramolecular hydrogen bonding decreases intermolecular interactions

CHROMATOGRAPHY: You run a TLC mixture of two unknown halogenated alkenes, but only see one spot with an Rf of 0.91, and you used ethyl acetate as the solvent. What went wrong?

Solvent is too polar

CHROMATOGRAPHY: You run a TLC mixture of a thiol and amine, but only see one spot with Rf of 0.15. Solvent was a mix of petroleum ether and dichloromethane. What went wrong?

Solvent isn't polar enough

CHROMATOGRAPHY: Rank these compounds in order of increasing Rf value: Naphthalene, o-toluic acid, fluorenol.

O-toluic acid < fluorenol < naphthalene

CHROMATOGRAPHY: Which has the larger Rf, 4-decanone or 4-decanol?

4-decanone

CHROMATOGRAPHY: Which has the larger Rf, xylene or benzoic acid?

Xylene

CHROMATOGRAPHY: Which has the larger Rf, cycloheptane or cycloheptanone?

Cycloheptane

CHROMATOGRAPHY: Why does ferrocene elute from the column first?

Less polar

CHROMATOGRAPHY: You run a column on a mixture of two unknown halogenated alkenes, but they both elute from the column at the same time. The solvent was dichloromethane. What went wrong?

Solvent was too polar

CHROMATOGRAPHY: You run a column with a mixture of naphthalene, o-toluic acid, and fluorenol. Solvent system is based on hexanes, but which becomes more polar with addition of increasing dichloromethane over time. Predict the elution order.

Naphthalene, fluorenol, o-toluic acid

POLYMERS: What is a molecule that may react chemically with another like molecule to form a larger molecule?

Monomer

POLYMERS: What is it called when a monomer is chemically linked together in a repeating fashion to form a polymer?

Repeating unit

POLYMERS: What is a large molecule called within which functional groups interact with other functional groups create weak bonds within the molecule?

Cross-linked polymer

DISTILLATION: Calculate the mole fraction of each component in solution if you mix 8.4 g of cyclohexane and 9.2 g of toluene.

0.5, 0.5

DISTILLATION: Equation that defines Raoult's Law.

P=X*Pp

DISTILLATION: Equation that defines Dalton's Law.

Ptotal = Pp1+Pp2

DISTILLATION: Calculate the mass of the oil (MW=169 g/mol) that co-distills with each one gram of water at 98ºC @ 1 atm pressure. (Vapor pressure of water @ 98º = 707.3 mmHg)

0.705 g

DISTILLATION: At 1 atm pressure, calculate the amount of water required to recover all of the oil (MW=169 g/mol) from 2g sample (5% oil by mass). (Vapor pressure of water = 707.3 mmHg)

0.14 g

DISTILLATION: One synthetic preparation of aniline (MW=93.19 g/mol) involves reducing nitrobenzene with iron and Hcl, and them steam distilling the resultant aniline at 99ºC. How much aniline co-distills with each gram of water? (Pwater @ 99ºC = 733.2 mmHg)

0.189

ENANTIOMERS: Equation that defines specific rotation.

[a] = a/lc

ENANTIOMERS: Equation that defines optical purity.

optical purity = measured [a]/[a] of pure * 100

ENANTIOMERS: What is the name for non-superimposable mirror image isomers?

Enantiomers

ENANTIOMERS: What must be done to the enantiomers before they can be separated?

Converted to diastereomers

ENANTIOMERS: What is the name of the racemic compound used in the resolution?

1-phenylethanamine

ENANTIOMERS: What resolving agent is used in this experiment?

L-(+)-tartaric acid

ENANTIOMERS: What is the instrument used to measure the optical rotation of your product?

Polarimeter

ENANTIOMERS: What is the name of the phenomenon when plane-polarized light passes through the solution of a single enantiomer, and the plane of polarized light is rotated?

Optical rotation

ENANTIOMERS: If a student obtains an amine with [a] = -35.3º, what is the optical purity of the amine? (Pure [a] is -40.3º)

87.59%

ENANTIOMERS: If a student obtains an amine with an optical purity of 87.59%, what are the %S and %R enantiomers of the amine in the sample?

93.8%, 6.2%

ENANTIOMERS: What optical rotation would be observed if 3.72g of the (S)-amine were mixed with 3.72g of the (R)-amine?

0

ENANTIOMERS: Calculate the specific rotation of a substance that is dissolved in a solvent (0.35 g/mL) and that has an observed rotation of -23º as determined with a 0.5 dm cell.

-131.4 (degrees)

ENANTIOMERS: Calculate the observed rotation of a substance that is dissolved in solution at 2.5 g/mL and is 75% optically pure. Assume a 1.0 dm cell is used. The specific rotation of the optically pure substance is +40º.

75 (degrees)

ENANTIOMERS: What is unique about diastereomers in regards to separation when compared to enantiomers?

Can be separated by physical methods

ENANTIOMERS: What are the two exceptions to enantiomers sharing physical and chemical properties?

Rotate polarized light in opposite directions, react at different rates