4.2.3 - Organic Synthesis Flashcards
What is organic synthesis?
Organic synthesis is the process of constructing organic compounds through a series of chemical reactions. This often involves the use of different reagents and conditions to transform simpler molecules into more complex ones.
What are the key steps involved in organic synthesis?
The key steps in organic synthesis are:
1- Selection of starting materials
2- Choice of reaction conditions (temperature, pressure, solvents)
3- Use of reagents (e.g., acids, bases, oxidizing agents)
4- Purification and separation of the desired product
What is meant by a synthetic route in organic chemistry?
A synthetic route is a sequence of chemical reactions used to transform a starting material into a desired product. The route includes intermediate compounds and reagents used at each stage.
What is a functional group interconversion (FGI)?
Functional group interconversion (FGI) is the process of changing one functional group into another. This can be achieved through various chemical reactions to modify the structure and properties of a molecule.
What is an example of a reaction that forms an alkene from an alkane?
Elimination reaction (dehydrohalogenation): An alkane can be converted to an alkene by removing a hydrogen atom and a halogen atom, often using concentrated sulfuric acid or potassium hydroxide (KOH) in ethanol.
Example:
CH₃CH₂Cl → CH₂=CH₂ + HCl (ethene is formed)
What reaction can be used to convert alkenes to alkyl halides?
Electrophilic addition reaction: Alkenes react with hydrogen halides (HX) to form alkyl halides.
Example:
CH₂=CH₂ + HCl → CH₃CH₂Cl (ethane chloride)
How do you convert a primary alcohol into an aldehyde?
Oxidation with an oxidizing agent like potassium dichromate (K₂Cr₂O₇) in acidic conditions will oxidize a primary alcohol into an aldehyde.
Example:
CH₃CH₂OH → CH₃CHO (ethanol to ethanal)
How can an aldehyde be converted into a carboxylic acid?
Aldehydes can be oxidized to carboxylic acids by using a stronger oxidizing agent such as potassium dichromate (K₂Cr₂O₇) under acidic conditions.
Example:
CH₃CHO → CH₃COOH (ethanal to ethanoic acid)
How can you convert a halogenoalkane into an alcohol?
Hydrolysis of a halogenoalkane with an aqueous sodium hydroxide (NaOH) solution undergoes a nucleophilic substitution to form an alcohol.
Example:
CH₃CH₂Cl + NaOH → CH₃CH₂OH + NaCl (ethanol is formed)
What is a Grignard reagent, and how is it used in organic synthesis?
A Grignard reagent is an organomagnesium compound (R-MgX) used in nucleophilic addition reactions. It is commonly used to form alcohols by reacting with carbonyl compounds (aldehydes or ketones).
Example:
CH₃CH₂MgBr + CH₃CHO → CH₃CH₂CH(OH)CH₃ (formation of a secondary alcohol)
How do you convert an alkyne into an alkene?
Hydrogenation can convert an alkyne into an alkene using hydrogen gas (H₂) and a nickel catalyst.
Example:
CH≡CH + H₂ → CH₂=CH₂ (ethene is formed)
How can you synthesize an ester from an alcohol and a carboxylic acid?
Esterification: An alcohol reacts with a carboxylic acid in the presence of an acid catalyst (e.g., sulfuric acid) to form an ester and water.
Example:
CH₃COOH + CH₃OH → CH₃COOCH₃ + H₂O (formation of methyl acetate)
What is the Wittig reaction, and what does it do?
The Wittig reaction is used to convert carbonyl compounds (like aldehydes or ketones) into alkenes by reacting with a phosphonium ylide.
Example:
C₆H₅CH=O + Ph₃P=CH₂ → C₆H₅CH=CH₂ + Ph₃P=O (formation of styrene)
What is the reduction of carbonyl compounds (like aldehydes and ketones) typically carried out with?
Reduction of carbonyl compounds can be achieved using sodium borohydride (NaBH₄) or lithium aluminum hydride (LiAlH₄) to form alcohols.
Example:
CH₃CHO + NaBH₄ → CH₃CH₂OH (reduction of ethanal to ethanol)
What is a nucleophilic substitution reaction?
A nucleophilic substitution reaction occurs when a nucleophile (a species with a lone pair of electrons) replaces a leaving group (such as a halide) in a molecule. This is common in reactions involving haloalkanes.
How do you convert a secondary alcohol to a ketone?
Oxidation of a secondary alcohol using an oxidizing agent like potassium dichromate (K₂Cr₂O₇) will convert the alcohol into a ketone.
Example:
CH₃CHOHCH₃ → CH₃COCH₃ (propan-2-ol to acetone)
What is reflux in organic synthesis?
Reflux is the process of heating a reaction mixture while continuously condensing the vapors and returning them to the reaction vessel. This prevents the loss of volatile substances and ensures the reaction proceeds at a constant temperature.
How can a carbonyl compound be reduced to an alcohol?
Reduction of a carbonyl compound (like an aldehyde or ketone) can be done using sodium borohydride (NaBH₄) to form a primary or secondary alcohol.
Example:
CH₃COCH₃ + NaBH₄ → CH₃CH(OH)CH₃ (acetone to isopropanol)
How can you synthesize an amine from a haloalkane?
Nucleophilic substitution of a haloalkane with ammonia (NH₃) forms an amine.
Example:
CH₃CH₂Cl + NH₃ → CH₃CH₂NH₂ + HCl (ethylamine)
What is the reduction of nitro compounds used for?
Reduction of nitro compounds (like nitrobenzene) using tin and hydrochloric acid (Sn/HCl) or iron and HCl forms amines.
Example:
C₆H₅NO₂ + 3H₂ → C₆H₅NH₂ (nitrobenzene to aniline)
