Organic Chemistry 2141 - Dorsey

impure samples melting point

display a decreased melting point and the melting point range is typically much larger.

Rf=

distance traveled by substance / distance traveled by solvent (dot/line)

A _____ point is determined by the equilibrium composition at which two compounds melt in a constant ratio.

eutectic point

what is temperature e?

eutectic point is the equilibrium point at which A and B melt in a constant ratio.

Explain the safety procedure that is used when chemicals are found in the eyes.

flush the eyes with water, if wearing eye contacts take them out, inform instructor/TA

GLC

gas liquid chromatography involves distributions between a mobile gas phase and a stationary liquid phase coated on a solid support

In polarimetry a (+) enantiomer rotates _____ around the plane of linearly polarized light and a (-) enantiomer rotates _______

+ = clockwise - = counterclockwise

When would we need to use fractional distillation instead of simple distillation?

when its (40-50%) of a difference between the 2 compounds.

List 2 reasons that a melting point of a compound may be lower than its known value.

1. A sample is impure if it has a melting point range that is lower and/or wider than that the literature value.More impurities increase this effect. 2. heating the sample too fast will give you poor results

Name 2 ways fractional distillation differs from simple distillation and how the affect the distillation process.

1. Transitions from vapor to condensing back to vapor and condensing again. this is because the condensors are different. One is packed one isn't. 2. Simple distillation is volatile and non volatile. Fractional is when 2 of the compounds have a 40-50% difference. 3. Fractional is vertical.

List two important guidelines when selecting the appropriate extracting solvent for an acid-base extraction.

1. extracting solvent must not react in a chemically irreversible way with the components of the mixture. 2. the extracting solvent must be immiscible or nearly so with the original solution.

Name 2 factors that can affect a compounds retention time.

1. it will pass through faster if its more volatile 2. boiling point of the mixture

Which method below will extract more solute from water: A. use 90ml of hexane and extract one time B. use 30 ml of hexane and extract three times. C. A and B are the same.

B

Which pair of chemicals will be well separated by simple distillation? A. Hexan (BP at 69C) and Toluene (BP at 111C) B. Acetone (BP at 56C) and Aniline (BP at 184C) C. Butyl acetate (BP at 126C) and Butanol (BP at 117C) D. all of the above

B more than a 40-50% difference

What is you IA's name?

Collin Bryant

When performing fractional distillation what type of compound is found in the liquid phase at any given temperature? A. highest BP B. more volatile C. most polar D. less volatile

D. less volatile

Why would one use fractional distillation instead of simple distillation?

When BP of the compounds have a 40-50% difference

When recrystallizing an impure solute under what conditions should the impurity be soluble. Explain.

When heated the impurity of the soluble should break down going from a solid into a liquid once the melting point is reached.

How can organic bases (amines) be converted to their salt form?

add hydrochloric acid. Go from a bas to a salt.

Why are Sn1 reactions preferred over Sn2 reactions on tertiary substrates?

because they tend to form more stable carbocations

When the pressure of the environment is much higher than 1 atm, the BP of water will be ____ than 100C.

higher

What is the difference between normal-phase and reverse-phase chromatography?

in reverse phase the packing material for the stationary phase consists of glass beads, and organic solvents are generally used as the eluting solvents where as in normal phase a polar stationary phase lick alumina or silica gel is used in combination with organic solvents as the mobile phase eluant.

Partial vapor pressure of a component in an ideal solution is _____ of the vapor pressure of other volatile components of the solution.

independent

pure compound

is a homogenous sample consisting only of molecules having the same structure

recrystallization

is a purification process by which crystals are grown slowly so as to incorporate only identical molecules that fit correctly into the crystal lattice

mobile phase

is generally the liquid or gas that flows continuously over the fixed stationary phase.

ideal solvent for recrystallization

is one that the compound to be recrystallized is soluble in at high temperature but is insoluble in at lower temperatures.

stationary phase

may be a solid or a liquid

The unique time it takes for a compound to exit the column after it is injected is called the ______

retention time

In last weeks lab, gas chromatography _____ was the stationary phase and ________ was the mobile phase.

metal column with a non polar coating atmospheric air

In a vernier gas chromatograph atmospheric air is the ______ while the metal column with a non polar coating is the ______

mobile phase stationary phase

The basis of separation for last weeks chromatography experiment involved differences in _____.In today's lab the basis of separation involves differences in ______.

polarity partitioning

Gas chromatography separates complex mixtures of substances based on _____ and _________

polarity volatility

In distillation process the ____ temp will be higher than the _____ temp because of the decreased _____ of the solution.

pot temp head temp vapor pressure

in todays lab what do the terms sn1 and sn2 stand for?

sn1= single first order substitution nucleophile sn2= double second order nucleophilic substitution.

The component that interacts with or binds more _____ to the stationary phase moves more _____ in the direction of the flow of the mobile phase.

strongly slowly

When doing a solution recrystallization if the solute has cooled and no crystals have formed the solution may be _________.

super saturated

Fractional distillation columns are often insulated to maintain a proper _____ across the length of the column.

temperature

To test your products last week, you performed two test on the products you obtained. The first was a silver nitrate test, and it tested for the presence of _____. The second test was a potassium iodide test and it tested for _______

tertiary halide primary

methods of chromatography dictate

the principle that the components of a mixture will distribute equally between two immiscible phases which is also the basis for separations by extraction.

Name all equipment names in distillation lab set up.

thermometer thermometer adapter distilling head pot two boiling chips electric flask heater support ring rubber tubing clamp condensor adapter receiver

TLC

thin layer chromatography s a form of solid liquid adsorption chromatography and is an important technique in organic chemistry for rapid analysis of small quantities of samples.

What is the purpose of the acid in SN1 and Sn2 reactions you will perform on t-butanol and 1-butanol today?

to see the protonation of the alcohol and how fast or slow it takes within each reaction