Synthesis routes Flashcards
How is the carbon chain extended when synthesising new compounds?
Refluxing the alkane with potassium cyanide in ethanol to form a nitrile. Turning the nitrile into an amide and then hydrolysing it, forming a carboxylic acid
Reducing a phenylketone
Reduce using NaBH4 to break the C=O bond and add 2 hydrogens
Aromatic amine + halogen
Replaces H with halogen at positions 2, 4, and 6
Amine + acid
N forms a dative covalent bond with the proton, making a quaternary salt
Amino acid carboxylic group + base
Water + sodium carboxylate salt
Amino acid carboxylic group + alcohol
Water + ester made from COOH of amino acid
Amino acid carboxylic group + metal ion
Metal carboxylate salt + hydrogen/CO2/water
Amino acid amine group + acid
Quaternary amine salt
Amino acid amine group + R-X
R added to nitrogen, H+ removed, H+ and X- left over
Primary amide + hot acid and water
Carboxylic acid + ammonium ion
Secondary amide + hot acid and water
Carboxylic acid + RNH3+
Primary amide + Hot OH- and water
Carboxylate + ammonia
Secondary amide + Hot OH- and water
Carboxylate + RNH2
Preparation of aromatic amines
Nitrobenzene + Sn + conc HCl under reflux => Phenylamine
ArNO2 + 6[H] + HCl => ArNH3+ + Cl- + 2H2O
ArNH3+ + Cl- + NaOH => ArNH2 + NaCl + H2O
Reduction of nitriles
A reducing agent turns the -C≡N group into -C-NH2 Agents: anhydrous LiAlH4: 4[H] anhydrous Na (alcohol): 4[H] Ni (catalyst): 2H2
How can you control the major product of the reaction between haloalkanes and ammonia?
Excess ammonia means the major product is the primary amine
Excess haloalkane means the major product is the quaternary salt
Formation of an aliphatic amine
Haloalkane + anhydrous ethanol + NH3 => Halide ion + Amine salt
Halide ion + amine salt + OH- => Amine + H2O + Halide ion
Extending the carbon chain
Reflux a solution of the haloalkane, potassium cyanide and ethanol
C-Cl becomes C-C≡N
C-C≡N can be reduced to an amine
H2O and H+ turns C-C≡N into CONH2
H2O and H+ turns CONH2 into COOH
CH3COOH + SOCl2 =>
Anhydrous conditions
CH3COCl + SO2 + HCl
Overall reaction of acyl chlorides (RCOCl)
RCOCl + HX => RCOX + HCl
HX can be water, an alcohol, phenol, ammonia, or an amine
What happens in the initiation stage of the halogenation of an alkAne?
The UV light splits the halogen molecule into 2 radicals (Br₂ => 2Br•)
What happens in the propagation stage of the halogenation of an alkAne?
Radicals react with non-radicals, building up the products of the reaction
C₂H₆ + Br• => •C₂H₅ + HBr
•C₂H₅ + Br₂ => C₂H₅Br + Br•
What happens in the termination stage of the halogenation of an alkAne?
The radicals come together to form stable products
2Br• => Br₂
2•C₂H₅ => C₄H₁₀
•C₂H₅ + Br• => C₂H₅Br
Hydrogenation of an alkEne
Converts alkEne to alkAne
C₂H₄ + H₂ => C₂H₆
150 degrees, nickel
Hydration of an alkEne
Acid and steam, produces an alcohol.
How do you determine the major product of a reaction between a hydrogen halide and an asymmetrical alkene?
Use Markownikoff’s rule: The hydrogen bonds to the carbon atom already bonded to the most hydrogens to begin with. This is because carbocations with other carbons bonded to the C+ are more stable, meaning they react less easily
What happens when a primary alcohol is fully oxidised by K2Cr2O7?
Water and a carboxylic acid are formed
What happens when a secondary alcohol is heated under reflux with K2Cr2O7?
Water and a ketone are formed
What happens when you gently heat a primary alcohol with an oxiding agent (such as K2Cr2O7), and distil immediately?
The alcohol is partially oxidised to an aldehyde, and water is formed
Describe esterification
An alcohol and a carboxylic acid react in the presence of an acid catalyst to form an ester. This reaction is slow and reversible.
What happens when an alcohol is heated with a strong acid?
The -H and the -OH are removed from the carbon backbone, forming water and an alkene
How are esters formed in the lab?
Alcohol and carboxylic acid mixed in test tube. Sulfuric acid is added and the tube is kept in a hot water bath
How are alcohols dehydrated in the lab?
Alcohol is heated under reflux with sulfuric or phosphoric acid for 40 minutes
How do hydrogen halides react with alcohols?
They form a haloalkane and water.
How can you predict the product of the dehydration of an alcohol?
Primary alcohol => One alkene
Secondary alcohol => Two alkenes (stereoisomers)
Tertiary alcohol => No reaction
Describe the nitration of benzene
Warm benzene is added to concentrated nitric acid and sulfuric acid. This releases electrophilic NO2+ ions into the solution. An electron from the delocalised electron ring in the benzene molecule bonds the NO2+ to one of the carbons. The H bonded to the same carbon donates its electron back to the delocalised ring and becomes a free H+ ion
How can you form a salt from phenol?
Phenol is weakly acidic, so it reacts with NaOH to form sodium phenoxide and water. It also does the same with sodium.
What are the conditions for making chlorobenzene?
Chlorine gas and solid aluminium chloride (completely anhydrous)
How is nitromethylbenzene produced from benzene?
Benzene requires nitration and alkylation. The nitro group is 3-directing, whereas the methyl group would be 2, 4 and 6-directing.
Describe the nitration of phenol
Phenol reacts with dilute nitric acid to form two isomers of nitrophenol, and water. Due to the increased reactivity of phenol compared to benzene, it doesn’t require a catalyst
What is Friedel-Crafts alkylation?
A reaction that puts an alkyl group (such as methyl) on a benzene ring using a haloalkane and a halogen carrier. The reaction is C6H6 + RX + AlCl3 => (reflux) C6H5R + HCl
What is Friedel-Crafts acylation?
A reaction that substitutes a H in benzene for an acyl group. The reaction is C6H6 + RCOCl + AlCl3 => (reflux) C6H5COR + HCl. If R is a hydrogen, the product is benzaldehyde, otherwise it’s a phenylketone
Carbonyl + acid + cyanide
=O becomes -OH, CN added
