organic chemistry I lab final

fume hood

ventilated workspace that removes hazardous vapours so you don't inhale anything toxic

eye wash station

station designed to flush eyes with water for at least 15 minutes after chemical exposure

MSDS/SDS

document that lists hazards, handling, disposal and first aid for chemicals

condenser

glass apparatus used to cool vapours back into liquid (via reflux or distillation)

hickman stillhead

distillation head used to microscale distillation to collect condensed liquid

pasteur pipette

narrow glass dropped used for transferring small liquid volumes

Hirsch funnel

small vacuum filtration used for microscale solids

Buchner funnel

flat bottom funnel used with vacuum filtration for LARGE amounts of solid.

separatory funnel

tear drop shaped glass tool for liquid-liquid extraction, the denser organic layer remains on top whilst the aqueous layer remains on the bottom

round bottom flask

flask that heats evenly

melting point

temperature range over which a solid becomes a liquid, it is also a purity indicator

melting point depression

lowered melting point due to impurities disrupting lattice

simple distillation

separation of liquids with large boiling point differences

fractional distillation

separation of liquids with close enough boiling points

steam distillation

distillation using steam to lower the boiling temperature of heat sensitive organic compounds

vacuum distillation

under reduced pressure to lower boiling points

acid base extraction

separation technique using protonation and deprotonation to move compounds between layers

drying agents

solids, such as MgSO4 and Na2SO4, that remove water from organic solutions

gravity filtration

uses gravity to remove solids from liquids

vacuum filtration

uses suction to rapidly isolate the solids

stationary phase

solid adsorbent that compounds stick too (silica/alumina), typically lower

mobile phase

solvent moves compounds along stationary phase, typically higher

rf value

distance traveled by compounds divided by distance traveled by solvent

elution order

least polar elutes first on silica gel

gradient elution

increasing the solvent polarity to force compounds off a column

ir absorption

frequency at which a bond vibrates due to IR radiation

fingerprint region

complex region around <1500 cm-1 unique to each molecule

chemical shift δ (HNMR)

position of NMR signal relative to reference, which depends on the electron environment

integration

area under the peak which is equal to the number of hydrogens

multiplicity/splitting

pattern based on neighbouring hydrogens -- n+1

coupling constant (J)

spacing between split peaks in Hz

doublet of doublet

proton coupled by two non equivalent neighbours

downfield

shift to the left -- desuhielded, electronegative atoms nearby

chemical shift (CNMR)

position of carbon signals, carbonyls high ppm, aliphatic low ppm

M+ peak

molecular ion peak = molecular mass

base peak

most intense peak and the the most stable fragment

how does polarity impact the Rf value?

more polar compounds = stick better to polar stationary phase, moving slower and getting LOWER RF values, less polar compounds = prefer the non polar mobile phase, moving faster for higher rF value

how do you choose the right amount of hexane and ethyl acetate to yield an RF value that reflects a good separation?

if the Rf values are too high == less polar solvent, more hexane, less ethyl acetate

if the Rf values are too low == use more polar solvent, less hexane and more ethyl acetate

what is the cm-1 of the O-H and what does it look like?

broad 3200-3600 cm-1

what is the cm-1 of the N-H and what does it look like?

sharper than O-H but still broad, 3300 cm-1

what is the cm-1 of the C=O bond and what does it look like?

~1700 sharp

what is the cm-1 of the C=C bond and what does it look like

~1650 cm-1

why is HCl used in acid base extraction

because it protonates the amines making them water soluble salts

why is H2SO4 used?

it is a strong dehydrating acid, commonly used in E1/E2 dehydrations of alcohols to form alkenes. it protonates carbonyls and epoxides to increase electrophilicity and it is a catalyst for esterfications

esterfication

alcohol and carboxylic acid combine with an acid catalyst to form an ester.

why do we use NaOH

it is a strong base useful for deprotonation, it removes acidic impurities in workups and used in basic epoxide openings

why do we use NaHCO3

neutralises acids and removes HBr, HCl or acids

why is br2 /CH2Cl2 used

tests for unsaturation (bromine test), electrophilic addition to alkene --> vicinal dibromine

why is HBr used

its used converts alcohols into alkyl bromines (SN1 or Sn2) strong acid + nucleophile in substitution labs

why is dichloromethane used

it is highly volatile, excellent organic solvent for extraction + reactions, non flammable, dissolves both polar and non polar organics

why is diethyl ether used

classic extraction solvent because it is immiscible with water H2O, good for grignards because it stabilises Mg species. Evaporate easily when isolating products.

why do we use ethanol/methanol

polar protic solvent for recrystallisation, washes glassware and crystals

why are hexanes used?

very non polar solvent for TLC and column chromatography, used in solvent gradients with ethyl acetate

why ethyl acetate used

moderately polar solvent for TLC, column chromatography, paired with hexanes for polarity tuning

why is MgSO4 used

fast, efficient drying of organic layers

why is Na2SO4 (Sodium Sulphate) used

it is gentle for drying and good for large volumes, doesn't clump as fast as MgSO4

why is KMnO4?

it is used for the Baeyer test for alkenes, strong oxidiser

why is sodium borohydride used (NaBH4) used

mild reducer for carbonyls (Aldehydes/Ketones), safe and selective

why is Sodium Thiosulphate used (Na2S2O3)

neutralises halogens, essentially after bromination tests

why is Brine, or saturated NaCl, used

salts out water from organic layer during extraction, helps break emulsions

how does Baeyer Test work?

1. KMnO4 is te oxidising agent, cold, dilute KMnO4 reacts with C=C double bonds, by adding hydroxyl groups across the pi bonds

2. the pi bond gets oxidatively cleaved

so the colour change is due to Mn changing its oxidation state

purple --> brown ppt means alkene sent

how do bromine tests work

1. Bromine is red/brown solution, Br2 dissolved in dichloromethane giving it a brown colour

2. Alkenes react instantly with Br2 and the pin bonds attack the Br2 forming the bromonium ion --> Br- attacks --> vicinal dibromide

positive test means alemen is present

reflux

heating a reaction mixture at its boiling point while continuously condensing the vapours back into the flask,

hot vacuum filtration

filtration performing while the solution is still hot using a vacuum source (Buckner or Hirsh funnel) it removes insoluble impurities from a hot solution before crystallisation, used to keep everything in solution EXCEPT the unwanted solids

recrystallisation

purification technique in which a solid dissolves in a hot solvent and them reforms crystals upon cooling -- isolates pure compounds based on solubility differences

extraction

separation of two immiscible liquids (aqueous + organic) that distribute compounds based on polarity and acid/base

distillation

Purification method that separates liquids based on boiling point differences. Isolate one liquid from another

Remove solvent

Column Chromatography

Technique that separates compounds based on polarity and affinity to the stationary phase (silica/alumina). Process:

Packs a column with silica (stationary phase)

Runs solvent (mobile phase) through it

Less polar compounds elute first; more polar stick longer

Drying Organic Solvent

Removing trace water from an organic layer after extraction using a drying agent (MgSO₄, Na₂SO₄). How it works:

Add drying agent → it binds water → forms clumps

When the solution looks clear and drying agent flows freely, it's dry Purpose:

Ensures solvent is water-free before evaporation or further reaction

limiting reagent

The reactant that is completely consumed first in a reaction, therefore determining the maximum amount of product that can form.

% Recovery

A measure of how much material you successfully recovered after a purification process (recrystallization, extraction, etc.). Formula:

%Recovery=mass recovered/original mass×100

% Yield

A measure of reaction efficiency, showing how much product you obtained compared to the theoretical amount based on the limiting reagent.

Stationary Phase

The solid material (usually silica or alumina) that stays fixed in place during TLC or column chromatography.Compounds interact with it based on polarity — the more a compound sticks, the slower it moves.

Mobile Phase

The liquid solvent that moves through/over the stationary phase in chromatography.Carries compounds along the stationary phase; polarity determines how fast compounds travel.

Eluent

The specific solvent or solvent mixture used as the mobile phase in chromatography.Choosing the right eluent controls separation quality (e.g., hexanes/ethyl acetate gradient).

NaI in Acetone Test

Tests whether an alkyl chloride or bromide can undergo SN2 substitution.

Positive: formation of white NaCl or NaBr precipitate Indicates a substrate that reacts SN2.

TLC Analysis (Thin Layer Chromatography)

Technique used to monitor reactions, assess purity, and compare mixtures. Relies on differences in polarity and adsorption to silica (stationary phase).

Key concepts:

Rf value: distance spot traveled / distance solvent front traveled

More polar compounds stay lower on plate

Mixtures show multiple spots

Reaction progress: disappearance of starting spot, appearance of product spot

IR Spectroscopy (Infrared Spectroscopy)

Technique that identifies functional groups by measuring bond vibrations when exposed to IR light.Each bond absorbs at a characteristic frequency (e.g., C=O ~1700 cm⁻¹, O-H ~3400 cm⁻¹).

GC-FID (Gas Chromatography)

GC separates the mixture, then the FID detector:

Burns the eluents in a small flame

Measures ions formed

Produces peak areas proportional to the amount of compound

FID gives:

percent composition)

great sensitivity for hydrocarbons But doesn't give molecular weight like MS does.