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A Level Chemistry Definitions > Organic Synthesis: Alcohols & Halogenoalkanes > Flashcards

Organic Synthesis: Alcohols & Halogenoalkanes Flashcards

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1
Q

The equation(s), reactants, reagents, conditions and, if necessary, catalysts, used for the following synthesis are:

PRIMARY and SECONDARY ALCOHOL → CHLOROALKANE

A

-For primary and secondary alcohols:

  • The white solid, phosphorus(V) chloride, PCl5 is added
  • The reaction is very vigorous, so heating of reaction mixture is not necessary
  • Nucleophilic substitution

CH3CH2CH2OH + PCl5 → CH3CH2CH2Cl + POCl3 + HCl

The two inorganic products are phosphorus oxychloride and hydrogen chloride

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2
Q

The equation(s), reactants, reagents, conditions and, if necessary, catalysts, used for the following synthesis are:

HALOGENOALKANE → ALCOHOL

A

-Reaction with water:

-Add water to the halogenoalkane
-Warm the mixture
-Hydrolysis (nucleophilic substitution)
CH3CH2Cl + H2O → CH3CH2OH + HCl

-Reaction with KOH or NaOH:

-Add an aqueous alkali such as potassium hydroxide to the halogenoalkane
-Heat under reflux, in aqueous solution
-Nucleophilic substitution (hydrolysis)
CH3CH2Cl + KOH → CH3CH2OH + KCl

Rate of reaction:
iodo > bromo > chloro > fluoro
The weaker carbon-halogen bond in iodoalkanes means a lower activation energy, so the fastest rate

tertiary > secondary > primary
Tertiary halogenoalkanes have more electron releasing CH3 of CH3CH2 groups which facilitate the release of the negative halide ion by ‘pushing electrons’ towards the halogen atom

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3
Q

The reactants, reagents, conditions and, if necessary, catalysts, used for the following synthesis are:

ALKENE → ALCOHOL

A

-Hydration of alkenes:

-Add gaseous water (steam) to the gaseous alkene
-Heat to 300°C at 60-70 atm pressure
-Phosphoric(V) acid catalyst, (H3PO4)
-Addition reaction
CH2CH2 + H2O → CH3CH2OH

When an unsymmetrical alkene, such as CH2=CHCH3 (propene) is used, the major product is :
CH2CHCH3 + H2O → CH3CHOHCH3
The more stable carbocation that forms is the secondary carbocation due to the presence of two electron releasing alkyl groups, so propan-2-ol is the major product

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4
Q

The equation(s), reactants, reagents, conditions and, if necessary, catalysts, used for the following synthesis are:

ESTER → ALCOHOL + CARBOXYLIC ACID

A

-Hydrolysis of esters in acidic solution to produce a carboxylic acid and an alcohol:

-Add water to the ester
-Add an acid catalyst, such as sulfuric acid
-Heat under reflux
CH3COOCH2CH3 + H2O ⇌ CH3COOH + CH2OHCH3
Reaction does not go to completion

-Hydrolysis of esters in alkaline solution to produce a carboxylate salt and an alcohol:

-Add aqueous sodium hydroxide
-Heat under reflux
CH3COOCH2CH3 + H2O → CH3COO-Na+ + CH2OHCH3
reaction goes to completion

the carboxylate salt is converted to an acid by adding a strong diluted acid, such as dilute H2SO4
CH3COO- + H+ → CH3COOH

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5
Q

The equation(s), reactants, reagents, conditions and, if necessary, catalysts, used for the following synthesis are:

ALCOHOL + CARBOXYLIC ACID → ESTER

A

-Esterification:

  • Mix the carboxylic acid with an alcohol
  • Small amount of an acid catalyst (often concentrated H2SO4)
  • Addition-elimination reaction

HCOOH + OHCH2CH3 ⇌ HCOOCH2CH3 + H2O
-the O in the H2O and one of the H comes from the OH in the carboxylic acid, while the other H comes from the OH in the alcohol

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6
Q

The equation(s), reactants, reagents, conditions and, if necessary, catalysts, used for the following synthesis are:

SECONDARY ALCOHOL → KETONE

A

-Oxidation of secondary alcohol:

  • Add potassium dichromate(VI) solution and dilute H2SO4 acid (to make acidified K2Cr2O7)
  • Heat under reflux

CH3CH2OHCH3 + [O] → CH3COCH3 + H2O

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7
Q

The equation(s), reactants, reagents, conditions and, if necessary, catalysts, used for the following synthesis are:

KETONE → SECODARY ALCOHOL

A

-Reduction of ketones:

-Add lithium tetrahydridoaluminate (also called lithium aluminium hydride), LiAlH4 to the ketone
-The LiAlH4 is dissolved in dry ether (ethoxyethane)
-Add an aqueous solution of an acid to protonate the O- in the first step of the reaction
CH3COCH3 + 2[H] → CH3CH(OH)CH3

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8
Q

The equation(s), reactants, reagents, conditions and, if necessary, catalysts, used for the following synthesis are:

ALDEHYDE → ALCOHOL

A

-Reduction of aldehydes:

-Add lithium tetrahydridoaluminate (also called lithium aluminium hydride), LiAlH4 to the ketone
-The LiAlH4 is dissolved in dry ether (ethoxyethane)
-Add an aqueous solution of an acid to protonate the O- in the first step of the reaction
CH3CH2CHO + 2[H] → CH3CH2OH

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9
Q

The equation(s), reactants, reagents, conditions and, if necessary, catalysts, used for the following synthesis are:

ALCOHOL → ALDEHYDE

A

-incomplete oxidation of a primary alcohol

  • Add potassium dichromate(VI), K2Cr2O7, and dilute H2SO4 acid
  • Distil with addition (heat the oxidising agent and slowly add the alcohol)

CH3CH2OH + [O] → CH3CHO + H2O

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10
Q

The equation(s), reactants, reagents, conditions and, if necessary, catalysts, used for the following synthesis are:

CARBOXYLIC ACID → PRIMARY ALCOHOL

A

-Reduction of carboxylic acid to primary alcohol

  • Add lithium tetrahydridoaluminate (also called lithium aluminium hydride), LiAlH4 to the ketone
  • The LiAlH4 is dissolved in dry ether (ethoxyethane)

CH3CH2COOH + 4[H] → CH3CH2CH2CH2OH + H2O

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11
Q

The equation(s), reactants, reagents, conditions and, if necessary, catalysts, used for the following synthesis are:

ALDEHYDE → CARBOXYLIC ACID

A

-Complete oxidation of primary alcohol

  • Add potassium dichromate(VI), K2Cr2O7, and dilute H2SO4 acid
  • Heat under reflux

CH3CH2OH + [O] → CH3COOH

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12
Q

The equation(s), reactants, reagents, conditions and, if necessary, catalysts, used for the following synthesis are:

ALCOHOL → BROMOALKANE

A

-For primary, secondary and tertiary alcohols:

-Add a mixture of potassium bromide and 50% concentrated sulfuric acid to the alcohol
-Warm the reaction mixture
(reaction of inorganic reagents)
2KBr + H2SO4 → K2SO4 + 2HBr
or
KBr + H2SO4 → KHSO4 + HBr

CH3CH2CH2OH + HBr → CH3CH2CH2Br + H2O

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13
Q

The equation(s), reactants, reagents, conditions and, if necessary, catalysts, used for the following synthesis are:

ALCOHOL → IODOALKANE

A

-For primary, secondary and tertiary alcohols:

  • Add a mixture of red phosphorus and iodine to the alcohol
  • Heat the reaction mixture with heat under reflux
  • Nucleophilic substitution

First, phosphorus(III) iodide is formed:
2P + 3I2 → 2PI3

3CH3CH2OH + PI3 → 3CH3CH2I + H3PO3
Phosphonic acid is formed along with the iodoalkane

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14
Q

The equation(s), reactants, reagents, conditions and, if necessary, catalysts, used for the following synthesis are:

TERTIARY ALCOHOL → CHLOROALKANE

A

-For tertiary alcohols:

  • Mix the alcohol (by shaking) with concentrated hydrochloric acid
  • Room temperature
  • Nucleophilic substitution

(CH3)3COH + HCl → (CH3)3CCl + H2O

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15
Q

The equation(s), reactants, reagents, conditions and, if necessary, catalysts, used for the following synthesis are:

HALOGENOALKANE → NITRILE

A

-For primary, secondary and tertiary halogenoalkanes:

  • Add aqueous potassium cyanide to the halogenoalkane
  • Heat under reflux the reaction mixture
  • Nucleophilic substitution

CH3CH2I + KCN → CH3CH2CN + KI

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16
Q

The equation(s), reactants, reagents, conditions and, if necessary, catalysts, used for the following synthesis are:

PRIMARY HALOGENOALKANE → PRIMARY AMINE

A

-For primary halogenoalkanes:

-Add excess ammonia gas to the halogenoalkane and seal the container
-Heat the sealed container (alternatively, use concentrated NH3 solution at room temperature)
-Nucleophilic substitution
Simplified equation:
CH3CH2CH2I + NH3 → CH3CH2CH2NH2 + HI

In fact, the NH3 is a base, so reacts with the acid HI to form a salt:
CH3CH2CH2I + NH3 → CH3CH2CH2NH3+ + I-
Here the product is a salt, not a primary amine, so excess ammonia is used:
CH3CH2CH2NH3+I- + NH3 → CH3CH2CH2NH2 + NH4+I-

The final equation is therefore:
CH3CH2CH2I + 2NH3 → CH3CH2CH2NH2 + NH4+I-

17
Q

The equation(s), reactants, reagents, conditions and, if necessary, catalysts, used for the following synthesis are:

NITRILE → CARBOXYLIC ACID

A

-In acidic conditions:

-Add a dilute acid, such as dilute HCl acid, to the nitrile
-Heat the mixture under reflux
CH3CH2CN + HCl + 2H2O → CH3CH2COOH + NH4Cl

-In alkaline conditions:

-Add sodium hydroxide to the nitrile
-Heat the mixture under reflux
CH3CH2CN + H2O + NaOH → CH3CH2COONa + NH3
-Add a strong, dilute acid, such as dilute H2SO4 or dilute HCl to obtain the free carboxylic acid
CH3CH2COO- + H+ → CH3CH2COOH

18
Q

The equation(s), reactants, reagents, conditions and, if necessary, catalysts, used for the following synthesis are:

ALKENE → ALKANE

A

-hydrogenation of alkenes

  • Add H2 gas
  • Heat to 150° C
  • Nickel catalyst
  • Electrophilic Addition reaction

CH2CH2 + H2 → CH3CH3

19
Q

The equation(s), reactants, reagents, conditions and, if necessary, catalysts, used for the following synthesis are:

CARBOXYLIC ACID → ACYL CHLORIDE

A

-Halogenation

-Add phosphorus(V) chloride, PCl5
-Anhydrous conditions (dissolve in dry ether) as PCl5 and the acyl chloride react with water
CH3CH2COOH + PCl5 → CH3CH2COCl + HCl + POCl3

the POCl3 mixes with the acyl chloride, so the mixture needs to be separated by fractional distillation. the HCl gas produced escapes as misty fumes

20
Q

The equation(s), reactants, reagents, conditions and, if necessary, catalysts, used for the following synthesis are:

CARBOXYLIC ACID → CARBOXYLATE SALT

A

-Neutralisation

-Add an aqueous solution of NaOH
CH3COOH + NaOH → CH3COO-Na+ + H2O

A Level Chemistry Definitions (39 decks)

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