Lab 1 – Cycloadditon of Dichlorocarbene to Cyclohexene
• Carbenes = intermediates with two single bonds and a pair of non-
bonding electrons on a carbon. They lack a pair of electrons to
complete a stable octet.
• Carbenes are electrophilic and extremely reactive.
• Can be done by thermal or photochemical decomposition of a
diazo alkane (R 2=N =N ) to give the carbene and nitrogen (N ). 2
• Can be generated by carbanion alpha to an alykl halide,
followed by alpha halide elimination. (Used to form
dichlorocarbene by chloroform and a base: remove a proton,
followed by alpha chloride elimination to give :CCl )2 Alpha
elimination is the elimination of the alpha halide, to create the
carbene. It is NOT PROTON ABSTRACTION.
• In presence of an alkene, there is addition of the carbene to the
double bond at the least substituted carbon.
• Carbenes react readily with anion (negative charge) and
• A two-phase transfer catalyst was used as the organic phase had
the alkene and carbene precursor, and the aqueous phase had the
• A phase transfer catalyst: has good solubility in both organic
and aqueous substances. Quaternary ammounium salts are
frequently used (organic in the organic layer, ammonium group in
the aqueous). Example: benzyltriethylammonium chloride,
trioctylmethylammonium chloride and tetrabutylammonium
• The phase transfer catalyst is converted to its hydroxide salt in the
presence of the base and this will equilibrate between the two
layers. The reaction will only occur at the interphase of the
• Used: NaOH (concentrated base 25M), chloroform
(dichlorocarbene precursor), cyclohexene (alkene),
benzyltriethylammnium chloride (phase-transfer catalyst), water,
• The phase transfer catalyst is hygroscopic, meaning it has the
ability to attract and hold water molecules from the environment,
and needs to be capped immediately and avoid contact with skin.
• When shaking the separatory funnel to create the emulsion, wear
gloves because the mixture is caustic, meaning it causes
• Any emulsion should be left in the AQUEOUS layer
• The phase transfer catalyst promotes reaction at the interface,
therefore an emulsion (a colloidal suspension of one liquid in
another) was kept for a long time to increase yield (by shaking we
increased the surface area).
• It was washed with ether to dissolve any 7,7-dichloronorcane
remaining in the aqueous layer because it is much more soluble in
ether than in water. • After being dried with anhydrous sodium sulfate, it is Roto-vapped.
At the point where it is evaporated down to 5-8mL, bubbles are no
longer observed in the R.B flask.
• Then subjected to simple distillation. At the final stage of simple
distillation, the condenser was subjected to air-cooling
instead of water because the final product apparently has
very high boiling temperature and we might crack the
condenser if we continue using water for cooling.
o Vacuum on briefly, and then turned off, collect first distillate
at variac setting of 45. When boiling slows, change receiver
flasks, turn on vacuum fully, and set variac to 80.
• The IR was taken to show a C-Cl stretch and no C=C.
Things/techniques to know:
Lab 2 – The Grignard Reaction
• Organometallic compound formed by reaction of an organic halide
with magnesium in ether.
• Grignard’s + aldehyde or ketone secondary or tertiary alcohol
and a new C-C bond.
• The purpose of crushing the magnesium turning is to clean the
surface and increase the active surface area of the turnings
(removed MgO and grease) so the metal can react to form the
• Saturated salt solution acts as a drying agent by removing
aqueous residue from the ethereal solution. Anhydrous sodium
sulfate also acts as a drying agent because it is hygroscopic
and acts as a dessicant.
• Wurtz coupling is the reaction between bromobenzene and
Grignard reagent to form biphenyl. Biphenyl is soluble in hexane
and is therefore removed as an impurity. Triphenylcarbinol is
soluble in ether, but not hexanes.
• Ether is used to stabilize the Grignard reagent, it is easy to
Rotovap, it has a high vapor pressure (to keep water out), and
helps to make the Grignard reagent soluble (therefore it goes from
murky to brown).
• A steam bath is used since ether is extremely flammable, so it is
• Anhydrous diethyl ether (absolute ether) is used and not
petroleum ether (mixture of alkanes) or regular ether (has water).
• Ether is added in two steps because the higher the concentration
of reactants, the more rapid the reaction (you don’t want to dilute
the reactants too early).
• 10% sulphuric acid and water are used to quench the reaction by
protonating the oxygen to make alcohol.
• Solid product, took the melting point and predicted purity.
Lab 3 – Oxidation of an Alcohol• Primary and secondary alcohols can be converted back to
aldehydes and ketones respectively, by oxidation.
• Care must be taken when converting a primary alcohol to an
aldehyde, so it is not further oxidized to a carboxylic acid. This can
be done by removing the aldehyde as it is formed
• A secondary alcohol can ONLY be made into a ketone.
• Four oxidizing mixtures are commonly used:
o Permanganate in basic solution (often potassium
permangante in sodium hydroxide, is a very strong oxidizer
and produce a carboxylic acid to primary alcohols, but still a
ketone for secondary alcohols.
o Chromic acid in water or acetic acid is a strong oxidizer, but
primary alcohols converted to aldehydes must be removed
as they are formed.
o Chromic acid in aqueous acetone