Chem Lab Final

Simple Distillation

Used for separation of two or more liquids with different boiling points

Distillation set up

Water flows IN from bottom part and OUT from top part. Use a regulator between power socket and heating mantle (to control amount of heat). Never have a closed distillation system

Liquid Liquid Extraction

Used for separation of solutes with different solubility in given solvents

Separatory funnel

Apparatus used for liquid-liquid extractions, make sure to vent the funnel when originally mixing liquids. Make sure the stopcock is closed. The top layer is the less dense (organic) layer and the bottom layer is the more dense (aqueous) layer. if using DCM it will be on the bottom

CaCl2

Common dry agent because its fast, has a high capacity, reacts with some organic compounds and good for drying tubes

Gravity filtration

A technique that utilizes gravity to separate solids from liquids by passing the mixture through a filter paper.

Percent recovery

final/initial x 100%

recrystallization

A purification technique used to separate and purify solid compounds by dissolving them in a suitable solvent and allowing them to crystallize. (mainly using heat and boiling and dissolving a substance to remove impurities, followed by cooling to form pure crystals.

Melting point

The temperature at which a solid becomes a liquid, indicating the phase transition of a substance.

Melting point range

The first point at which you see a miniscus start to form and then the last point is when the sample is completely liquid

Liquification point

the temperature at which a sample starts to melt

TLC:Stationary phase

solid absorbent sometimes can be silica gel

TLC: mobile phase

Liquid solvent

TLC (thin layer chromatography)

can be used to:

• identify unknown substances and unknown compounds of mixtures

• to determine the best solvent for column chromatography

• to determine whether a substance is purified by recrystallization or another method still contains appreciable amounts of impurities

TLC: Solvent front

Distance that the mobile phase travels on the stationary phase. Always mark solvent front

TLC Visualization

Observe the TLC plate under ultraviolet light

RF calculation

RF = distance traveled by spot / distance traveled by solvent

Stereochemistry: Plane polarized light

Light that is passed through a polarimeter

Observed rotation

The angle by which a sample of an optically active substnace rotatied the plane of that beam

Polarimetry

movement of the angles of the observed rotation

Stereochemistry equations

Enantiomeric excess

EE = observed rotation / observed rotation of pure enantiomer X 100%

Extinction point

when light is blocked out so its intensity is at a minimum

Free Radical Bromination: Statistical Factor

Determined by the number of hydrogen atoms whose replacement will give a specific constitutional isomer

Free radical bromination: energy factor

related to the strength of the type of C-H bond being broken and is called the relative reactivity

Aliphatic

Hydrogen bound to sp3 hybridized carbons. can be primary, secondary, or tertiary depending on the number of other carbon atoms attached to the reference carbon atom

Allylic/Benzylic

When a hydrogen is attached to a sp3 hybridized carbon that is bound to a vinylic or aromatic carbon

Vinylic/aromatic

hydrogens attached to sp2 hybridized carbons

Acetylenic

hydrogens bonded to an sp hybridized carbon atom

Free radical bromination mechanism

Free radical bromination results

the compounds that had structures that contained only aliphatic hydrogens did not experience bromine discoloration during the allotted observation time, whereas the ones with benzylic or benzylic and aliphatic hydrogens did react during the allotted observation time

Alkylation of saccharin: reaction

a reaction involving oxygen as the nucleophile should occur faster than one involving nitrogen as the nucleophile becuase oxygen is more electornegative than nitrogen

Alkylation of saccharin:DMF

DMF should be used for this experiment because:

• it does not solvate the nucleophile strongly, leaving it free to attack the substrate

• solvation reduces the strength of a nucleophile and its rate

Alkylation of saccharin: How to get grams from mmol

10mmol x 1 mol / 1000 mmol x 205g / 1mol = 2.05 g sodium saccharin

percent yield

actual yield / theoretical yield x 100

Markovnikov

the H atom will always bond to the C with more H

Zaitsev product

the more higly substituted alkene that results from an elimination reaction

Dehydration of alcohols: mmol to g

150mmol x 1mol / 1000ml x 114.2g/1mol = 17.13g

Dehydration of alcohols: g to ml

Use density : 17.13 g x 1ml/0.93g = 18.6 ml

Dehydration of alcohols: Chromatogram

first high peak = initial boiling point

second high peak = final boiling point

Dehydration of alcohols: percentage of each product

1. calculate area for each peak corresponding to each of the two products

2. sum up the areas

3. the percentage of given product will equal the area of the peak corresponding to given product divided by the sum of both the areas

4. multiply by 100 to get a percent

Anti addition

addition form opposite sides of the double bond

syn addition

addition from the same side of a double bond

bromine and acetone

DO not mix them, will create tear gas/bromoacetone

Bromination of Cinnamic acid: ml to mmol

10ml x 3.12g/1ml x 1mol/159.8g x 1000mmol/1mol = 195.2 mmol of bromine.