Chemistry: Organic Chl

What does phenol not react with?

Na₂CO₃

Reagent for amine to ammonium chloride salt

HCl(aq)

Reagent for ammonium chloride salt to amine

NaOH(aq)

R+C: amide (NO₂) → amine (NH₂)

1) Tin (Sn) and conc HCl, heat under reflux (forms ammonium salt)

2) Neutralise with NaOH(aq)

Formation of electrophile in nitration of benzene

HNO₃+ H₂SO₄→ NO₂⁺+HSO₄^-+H₂O

End point observation for titration with iodine

Starch indicator causes colour change from blue/black to colourless

R+C: Haloalkane → Amine

Excess ethanolic NH₃

R+C: Haloalkane → Nitrile

Ethanolic NaCN/KCN

Acid anhydride + primary alcohol (inc. phenol) →

Ester + Carboxylic acid

Acid anhydride + COOH →

R+C: Carboxylic acid → Acyl chloride

SOCl₂

R+C: Acyl chloride → Carboxylic acid

H₂O

What happens when acyl chlorides and acid anhydrides react in hydrous conditions?

Forms carboxylic acids

R+C: Carboxylic acid → haloalkane

NaBr(aq)

Acyl chloride + (2NH₃)/Amide →

Amide + ammonium salt (HCl+NH₃→NH₄Cl for 2NH₃)

-OH directing effect

2,4- directing (electron donating group)

-NH₂ directing effect

2,4- directing (electron donating group)

-NO₂ directing effect

3- directing (electron withdrawing group)

What is the use of CDCl₃?

Use as a solvent that won’t affect the spectrum to dissolve solids

What is the use of D₂O?

Will remove -OH and -NH peaks as H is exchanged for deuterium

What is the use of tetramethylsilane, (CH₃)₄Si?

To provide a reference peak

How does gas chromatography work?

Stationary phase: liquid adsorbed on inert solid/ solid on solid support

Mobile phase: gas

Retention time depends on:

• high boiling point (longer RT)

• greater solubility in liquid phase (longer RT)

In summary the more affinity a substance has for the liquid or solid in the stationary phase, the longer the retention time and higher peak on mass spec.

Radical substitution mechanism to show Cl^* catalysing breakdown of ozone

Radical substitution mechanism to show how nitrogen monoxide radicals catalyse breakdown of ozone

Trend in reactivity of haloalkanes

Bond enthalpy decreases down the table as carbon-halogen bond strength decreases. This means iodoalkanes are the most reactive (least energy needed to break bond)

Effect of infrared radiation on covalent bonds

Cause them to absorb energy and vibrate more

Why are alkanes unreactive?

They have a high bond enthalpy and low polarity of sigma bonds

R+C: Nitrobenzene → phenylamine

Sn, conc HCl, reflux

R+C+M: Aldehyde/Ketone → Hydroxynitrile

NaCN, H₂SO₄, nucleophilic addition

R+C: Benzene → nitrobenzene

Conc HNO₃, conc H₂SO_4, heat 50-55 degrees C

R+C: Benzene → Alkylbenzene

Haloalkane, AlCl₃ catalyst, reflux

Where do curly arrows go from?

• Centre of covalent bond

• Lone pair

• Delocalised Pi system in benzene

Are balancing numbers included in atom economy?

YES

Limitations of radical substitution

• waste products in termination

• further substitution may occur

• substitution can occur anywhere on the chain to form structural isomers

Dipoles in C-Halogen bond

Halogen has negative dipole as is more electronegative than carbon

Test to measure the rate of hydrolysis of haloalkane

• Add AgNO₃ to haloalkane

• Time taken to form AgX precipitate

• Rate is 1/time

Describe trend down group of rate of hydrolysis of haloalkane

• Rate increases down the group (iodoalkanes hydrolysed faster than chloroalkanes)

• C-I bond is weakest as difference in electronegativity is smallest

Initiation and propagation steps of CFCs breaking down ozone

Why is the breakdown of ozone by CFCs bad for humans?

O₃ + O → 2O₂ (catalysed by chlorine radicals)

This is irreversible so ozone cannot reform. Less ozone means more UV penetrates and causes skin cancer

Why is benzene less reactive than alkenes?

• In benzene there are 6 delocalised electrons and there are 2 localised in alkenes

• The alkene double bond is more electron dense than pi-system

• Benzene is less able to polarise electrophiles so less susceptible to attack

Test for phenol

Br₂ (aq) is decolourised (orange to colourless) and white precipitate is formed

Why does phenol not react with sodium carbonate?

Too weak of an acid to react with weak bases

R+C: Phenol → nitrophenol

Dilute HNO₃, no catalyst required, RTP

How many moles of reducing agent [H] are needed to reduce aldehyde or ketone to alcohol?

2 [H] (no H₂O)

How are short chain carboxylic acids more soluble in water?

Able to form hydrogen bonds with water molecules

Acyl chloride + NH₃ →

Primary amide + HCl

Acyl chloride + primary amine →

secondary amide + HCl

Acyl chloride + secondary amine →

tertiary amide + HCl

Acyl chlorides + phenol →

phenyl ester + HCl (g)

How do amines act as bases?

Can accept H⁺ ions using lone pair on N forming a dative covalent bond to form an ammonium salt

Equation for reduction of NO₂ to NH₂

NO₂ + 6[H] → NH₂ + 2H₂O

Equation for reduction of nitriles to amines

CN + 2H₂ → CH₂NH₂ (2 moles of H₂ needed)

Which amino acid does not show optical isomerism?

Glycine (H for R-group)

Calculating the number of optical isomers in a molecule

2ⁿ where n is the number of chiral carbons

In which reactions are HCN or NaCN/KCN used?

NaCN and H₂SO₄ however HCN is made in situ is used in both carbonyls and haloalkanes (ethanolic) to nitriles

Products of acid hydrolysis of polyester

Carboxylic acid and alcohol

Products of acid hydrolysis of polyamide

Carboxylic acid and protonated amine

Products of alkaline hydrolysis of polyester

Carboxylate salt and alcohol

Products of alkaline hydrolysis of polyamide

Amine and carboxylate salt

Why are condensation polymers better for the environment than addition polymers?

Condensation polymers can be hydrolysed so are biodegradable, whereas addition polymers are not

Solutions to non-biodegradable addition polymers

• developing photodegradable polymers

• can be converted to monomers and used as chemical feedstock

• can be combusted for energy use (not if chlorine present as HCl (g) is toxic)

How to obtain pure dry liquid from organic synthesis

• If acid used then neutralise with Na₂CO₃ (aq) and release gas from tap of separating funnel

• separate layers according to density

• add drying agent e.g. MgSO₄ to remove any aqueous

• redistill and collect fraction at boiling point

Obtain a pure dry solid from organic synthesis

• recrystallise by dissolving crystals in the minimum volume of hot solvent

• allow to cool and crystals to form

• filter under reduced pressure

• wash and allow crystals to dry

If there is a liquid that needs testing for purity by chromatography, what method would be used and explain how it works

Gas chromatography is used and solubility is measured by relative solubility in mobile phase. The retention time is the time from injection to detection. Compare retention time to known value

What does the area under the peak for gas chromatography indictate?

Area is proportional to amount of components in the sample. Relative proportions are measured by dividing area under peak by total area under all peaks.

What charge do fragment ions have in mass spectroscopy

1+

What molecule is this?

Carboxylic acid

What molecule is this?

Alcohol

What molecule is this?

Aldehyde/ketone/ester

What does RPA 4 mean on aromatic peak on H-NMR spectroscopy

The benzene ring is disubstituted

R+C: Alkane → Haloalkane

Halogen , UV light, radical substitution

R+C: Alcohol → Haloalkane

NaOH, H₂SO₄, heat

R+C: Nitrile → carboxylic acid

HCl (aq), heat

R+C: Alkylation of benzene

CH₃Cl, AlCl₃