ochem lab unit 9

benefits of using microscale equipment

• less waste product

• less money spent on reagents

drawback of using microscale equipment

losses are magnetized

purpose of stir bar (peanut magnet)

to induce collisions between reagents

purpose of refluxing alcohol and acid

to provide heat required for reaction

purpose of "organic aerobics"

thorough mixing of immiscible layers

why did two layers form during the extractions

the liquids used were immiscible

purpose of anhydrous sodium sulfate to vial

acts as drying agent to absorb leftover traces of water and then turn into clumpy crystals

gas chromatography definition

system of separation using a mobile and stationary phase
- mobile phase is inert gas

purposes of running gas chromatography (3)

• determine number of components in mixture

• relative polarities of components

• percent composition

percent conversion indicates

whether or not a reaction went to completion

percent composition indicates

the relative proportions between major, minor, and trace

reflux definition

a lab technique in which one heats a reaction vessel to the boiling point and holding it there without the loss of any solvent

effect of inadequate or no stirring on percent conversion

not enough collisions to get to 100% conversion

*effect of inadequate or no stirring on IR and GC

observation of peaks in both starting materials and products

purpose of sodium bicarbonate in extractions

neutralize residual acid

observations in IR

peaks

deductions in IR

functional groups

extraction definition

lab technique used to separate two solutes with opposite polarities by mixing well to allow solutes to migrate into its respective layers to then be separated

observations in GC (3)

• retention time

• area under curve

• number of peaks

deductions in GC (3)

• relative polarity

• percent composition and conversion

• number of components in mixture

comparable value in TLC to retention times in GC

Rf: both indicating relative polarity

comparable value in TLC to number of peaks in GC

number of spots: both indicating number of components in the mixture

density

grams/mols

1000 μL

1 mL

% yield

actual/theoretical x 100

lower amount of SM on accident leads to

lower value than reality

% composition and % area

specific area/total area x 100

(?) greater area assigned to

major product

2-methylcyclohexanol boiling point

~165°

1-methylcyclohexene boiling point

~110°

3-methylcyclohexene boiling point

~104°

methylene cyclohexane boiling point

~102°

why is boiling point of the starting material higher than products

hydrogen bonding between alcohol molecules

effect of reflux temp >90°

loss of products through boiling

effect of reflux temp

incomplete reaction

acid catalyzed dehydration

H+, H2SO4, H3O+heat

(?) 3,3-dimethyl-2-hexanol major product

2,3-dimethyl-2-hexene

yield

(area %)(actual yield)/100

solving for starting materials from theoretical yield

theoretical/expected % yield

synthesis: yes completion: no
GC results

3 peaks for products and peaks for alcohol (high retention times)

synthesis: yes completion: no
IR results

OH alc and CO bonds from starting materials not lost in the product spectrum