Hydroxy compounds Flashcards
State different way in which alcohols can be produced
- electrophilic addition of alkenes
- oxidation of alkenes
- nucleophilic substitution of halogenoalkanes
- reduction of aldehydes and ketones
- reduction of carboxylic acids
- hydrolysis of esters
reaction, conditions, reagents
State two reactions of how alcohols are produced with alkenes
- ELECTROPHILIC ADDITION OF ALKENES
alkene + H2O(g) —> alcohol
conditons: Heat and H3PO4
reagants: alkene and steam - OXIDATION OF ALKENES
alkene + H2O + [o] —> Diol
conditions: Cold dilute KmNO4
Shaking of reagants
Reaction, condition, reagnants
How are alcohols formed from halogenoalkanes
NUCLEOPHILIC SUBSITUTION OF HALOGENOALKANES
Halogenoalkane+NaOH—> Alcohol + NaX
Conditions: Aqueous NaOH, Heat
Eg: HCH2CH2Br+NaOH —> HCH2CH2OH + NaBr
How are alcohols formed from carbonyls
REDUCTION OF ALDEHYDES AND KETONES
1. reduction of aldehydes
aldehydes + 2[H] —> primary alcohol
2. reduction of ketones
ketones + 2[H] —> secondary alcohol
Conditions: LiAlH4/ NaBH4
How are alcohols formed from carboxylic acids?
Reduction using LiALH4
carboxylic acid + 4[H] —> alcohol + H2
NaBH4 is too mild to use here.
How are alcohols produced from esters
Hydrolysis of esters with dilute acid/alkali
1. ACID
ester + H2O (H+ aq) ⇋ carboxylic acid + alcohol
conditions: heat and dilute acid
2. ALKALI
ester + NaOH —> Salt + alcohol
conditions: heat and alkali
eg- ethyl ethanoate + NaOH —> Sodium ethanoate + Ethanol
Reaction of Alcohols
- combustion
- substitution
- reaction with Na
- oxidation
- dehyrdation
describe the combustion of alcohols
Alcohol + Oxygen —> Carbondioxide + Water
Conditions: Heat
Eg: CH3CH2OH + 3O2 —> 2CO2 + 3H2O
product, reagents, conditions
Describe substitution of alcohols
HX + alcohol —> Halogenoalkane + H2O
KBr + H2SO4/H3PO4—> HX + alcohol —> Halogenoalkane + H2O
PCl3 + 3 alcohol —> 3 Halogenoalkane + H3PO3
Condition: Heat
PCl5 + alcohol —> Halogenoalkane + HCl + POCl3
Condition: r.t
SOCl2 + alcohol —> Halogenoalkane + HCl + SO2
Describe reaction of alcohol with sodium
alcohol + sodium —> sodiumalkoxide + H2
if excess ethanol evaporates white ppt of sodiumalkoxide can be seen
Eg: 2 CH3CH2OH + 2Na —> 2 CH3CH2O- Na+ + H2
State the oxidising agents, their color before and after oxidation
Acidified K2Cr2O7: Orange in color
When oxidised: Green
Acidified KMnO4: Purple
When oxidised: Colourless
state the products of alcohol oxidations and the conditions
primary alcohol -> aldehydes+ H2O
secondary alcohol -> ketones + H2O
teritiary alcohol -> dont oxidise
conditions: heat
reagants: oxidising agent
Describe the collection of alcohols upon oxidising
primary alcohols when oxidised= aldehydes
aldehydes are distilled off
if not, then further reflux = Carboxylic acid
Ketones cannot be oxidised
Describe the dehydration of alcohols
Reaction type: elimination reaction
alcohol—> alkene +H2O
Conditions: Heat and Al2O3 catalyst
alkene as gas, therefore collected over water
Describe esterification of alcohols
reaction type: condensation reaction
alcohol + carboxylic acid —> ester + H2O
conditions: heat under reflux
strong acid catalysts: H2SO4/ H3PO4
State the products when propanoid acid reacts with ethanol
propanoic acid + ethanol –(H2SO4)–> ethyl propanoate + H2O
alcohol name comes first when naming esters
State the classification of alcohols
Primary alcohols: (C with OH) Attached to 1 alkyl group
Secondary alcohol: (C with OH) Attached to 2 alkyl group
Teritiary alcohol: (C with OH) Attached to 3 alkyl group
Explain how iodoform can help with testing of alcohols. State which alcohol.
Secondary alcohol can be tested to find the position of OH group.
iodoform reacts with Methyl Ketones: CH3CO- GROUP
- Secondary alcohol is oxidised to form a methylketone
HALOGENATION:
Reagants: I2NaOH (Aq) - The carbonyl compound is halogentated: H atoms replaced ith I atoms: CH3—> CI3
HYDROLYSIS:
Reagants: NaOH (Aq) - This intermediate is hydrolysed forming a sodium salt and a triiodomethane (CHI3) : Which is a yellow ppt.
- If no yellow ppt formed alcohol may not be next to a methyl group but instead to an ethyl group or some other group.
state the acidity of alcohols in terms of dissociation in water
Weaks acids: They do not dissociate completely
ROH ⇌ RO- ( Alkoxide ion) + H+ ( hydrogen ion)
equillibrium shifts to the left therefore more alcohol than H+ ions
which is more acidic water or alcohol? why?
Water is more acidic
Alcohols:
- The alkoxide ion (RO⁻) has an alkyl group that donates electrons to oxygen.
- This increases oxygen’s electron density, making it more attracted to H⁺.
- As a result, the alkoxide ion reacts with H⁺ to reform the alcohol:
ROH ⇌ RO⁻ + H⁺
Water:
- The hydroxide ion (OH⁻) doesn’t have an alkyl group.
- This means less electron density on oxygen, so it’s less attracted to H⁺ compared to an alkoxide ion:
H₂O ⇌ HO⁻ + H⁺
(R is an alkyl group.)
what is the inductive effect
alkyl groups are electron donating, therefore they donate electron to stabalise the carbon bonded to them—> Positive inductive effect
