4.3 - Alcohol and Phenols Flashcards
What is the difference between a primary, secondary and tertiary alcohol?
Consider the carbon atom which the alcohol group (-OH) is bonded to:
● If this carbon is bonded to only one other carbon, then it is called a
primary alcohol.
● If this carbon is bonded to two carbons, then it is called a secondary alcohol.
● If this carbon is bonded to three carbons, then it is called a tertiary alcohol.
- Secondary Alcohol
What type of reaction can a halogenoalkane undergo to form an alcohol?
Nucleophilic substitution
What reactants and conditions are required to form ethanol from bromoethane?
Warm aqueous sodium or potassium hydroxide (NaOH(aq) or KOH(aq))
Draw the mechanism for the reaction which takes place between chloromethane and warm aqueous sodium hydroxide
What acts as the nucleophile in the reaction between chloroethane and warm aqueous sodium hydroxide?
The hydroxide ion from sodium hydroxide: OH-
What is the classification of the alcohol formed if 2-bromo-2-methylbutane undergoes nucleophilic substitution with KOH?
Give the reactants and conditions required for the formation of a hydroxynitrile from an aldehyde/ketone
Potassium or sodium cyanide is added to sulfuric acid to produce hydrogen cyanide.
Temperature of 20oC.
Why is hydrogen cyanide not added directly to an aldehyde/ketone for a nucleophilic addition reaction?
Hydrogen cyanide is a very poisonous gas.
Draw and name the mechanism for the formation of 2-hydroxypropanenitrile from ethanal and hydrogen cyanide
Name the type of reaction for the formation of alcohols from aldehydes and ketones
Reduction
What is the classification of the alcohols formed by the reduction of aldehydes and ketones?
Aldehydes will be reduced to primary alcohols.
Ketones will be reduced to secondary alcohols.
Give a reducing agent for the reduction of aldehydes and ketones to alcohols
NaBH4 dissolved in water with methanol
Write the chemical equation for the reduction of propanone to propan-2-ol
CH3COCH3 + 2[H] → CH3C(OH)HCH3
Name the mechanism for the reduction of propanal to propan-1-ol
Nucleophilic addition
What reagent is required to reduce carboxylic acids to alcohols?
LiAlH4
Why is NaBH4 used for the reduction of aldehydes and ketones but not for carboxylic acids?
NaBH4 is not reactive enough to reduce carboxylic acids.
Why are primary and secondary alcohols useful for organic synthesis reactions?
The -OH functional group is able to react with various different compounds.
What type of organic product is produced in the reaction between alcohols and hydrogen halides?
Halogenoalkanes
What catalyst is required for the reaction of primary and secondary alcohols with hydrogen chloride?
Anhydrous zinc chloride
What are the reagents required for the reaction of ethanol to form bromoethane?
Instead of directly adding hydrogen bromide, ethanol requires a mixture of potassium or sodium bromide and concentrated sulfuric acid. This will produce the hydrogen bromide which will react with ethanol to form bromoethane
What reagents are required to replace the -OH group with an iodide atom?
Sodium or potassium iodide is reacted with concentrated phosphoric acid. This produces hydrogen iodide which reacts with the alcohol, replacing the -OH group with an iodine atom.
What is the IUPAC name for the product of the reaction between 2-methylbutane-1,3-diol and excess hydrogen bromide?
1,3-dibromo-2-methylbutane
Name the mechanism for the reaction between acyl chlorides and alcohols
Nucleophilic addition-elimination
Draw the mechanism for the reaction between ethanoyl chloride and methanol
What is formed when an alcohol reacts with a carboxylic acid?
An ester
What is the functional group of an ester?
-COO-
What condition and catalyst is required for an esterification reaction?
The alcohol and carboxylic acid must be heated in the presence of a strong acid catalyst, e.g. concentrated sulfuric acid.
Give the chemical equation for the reaction between ethanoic acid and ethanol
CH3COOH + CH3CH2OH → CH3COOCH2CH3 + H2O
Name the ester formed in the reaction between butanoic acid and propanol
Propyl butanoate
What are the identifying properties of esters?
Esters are sweet smelling compounds which are often used in flavourings and perfumes. They have low boiling points and make good solvents for other polar molecules.
What is phenol?
What is the acidity of phenol?
Phenol is very weakly acidic. It has a pH between 5 and 6.
What can be observed when phenol reacts with bromine?
The bromine water will decolourise and a white precipitate will form.
Why does phenol generally react more readily than benzene?
The increased reactivity of phenol is because of the lone pair of electrons on the oxygen atom. This electron pair is delocalised into the ring structure. This increases the electron density of the ring, making it more susceptible to attack from electrophiles.
Considering the acidity of phenol, does phenol react with NaOH or Na2CO3?
Phenol will react with NaOH but since it is only weakly acidic it will not react with Na2CO3.
What is the IUPAC name of the product formed when phenol reacts with ethanoyl chloride?
Phenyl ethanoate
Give the chemical equation for the reaction between phenol and ethanoyl chloride
Give the chemical equation for the reaction between phenol and bromine
Describe the test for phenols
Aqueous ferric chloride (FeCl3) can be used to test for the presence of phenols. Compounds containing phenols will cause the solution to turn a vivid purple, blue, green or red colour - depending on the nature of the phenol.
What is the observed colour change when ferric chloride is added to phenol?
On the addition of ferric chloride, the solution will turn a vivid violet-purple colour.
