Hydroxy - incomplete

Question 1

Alcohols vs phenols

Answer 1

Alcohols have -OH grp NOT directly attached to a benzene ring (sp3 C)

Phenol have -OH grp directly attached to a benzene ring (sp2 C)

Question 2

General formula of hydroxy (not very useful)

Answer 2

CnH2n+1OH

Question 3

Pri, sec & ter alcohol

Answer 3

Primary - 1 R grp on the C that -OH is attached to

Sec - 2 R grp on the C that -OH is attached to

Ter - 3 R grp on the C that -OH is attached to

Question 4

Alcohol bp vs alkanes bp

Answer 4

Alcohol bp is much higher than those of alkanes of similar no. of e-

Reason: Larger amt of energy is needed to overcome the stronger hydrogen bonds b/w the alcohol molecules than the weaker (id-id) dispersion forces b/w the alkane molecules

Question 5

Factors affecting bp of alcohols (3) + reasons

Answer 5

1. Length of alkyl chain: bp increases as alkyl chain increases.
   Reason: Size of the e- cloud increases as the length of the alkyl chain increases. More energy required to overcome the stronger idid forces b/w alcohol molecules
2. Branching: Branching of carbon skeleton lowers bp
   Reason: Molecules become more spherical and compact. Lower SA for e- clouds and id-id forces are weaker
3. No. of -OH grps: bp increases with increase in no. of -OH grps
   Reason: Leads to more extensive Hydrogen bonding. Increases the bp of alcohols.

Question 6

Steps to arrange alcohols in order of increasing bp (3)

Answer 6

1. no. of -OH grps
2. no of e (check no. of C)
3. branching

Question 7

Solubility of alcohols in water

• alcohols vs alkanes
• 2 factors affecting

Answer 7

Alcohols more soluble than alkanes as they are able to form H bonds with water

However, solubility decreases as the no. of C atoms increases as the the hydrocarbon portion is np and as the C chain increases:

• id-id interactions b/w alcohol molecules becomes stronger and predominant
• Np hydrocarbon chain interferes with hydrogen bonding b/w H2O and alcohol molecules

BUT increase in no. of OH- grps increases no. pf H bonds the alcohol can form in water -> more soluble

E.g.: The presence of -OH grps allows the molecule to form extensive H bonding with water. This releasees sufficient energy to compensate for the energy needed to break the H bonds in pure water and in pure sucrose. Hence, sucrose is soluble in water.

Question 8

Solubility in org solvents + reason for acting as solvents that dissolve…

Answer 8

Miscible with most org solvents - as the hydrocarbon portions cans interact with the hydrocarbon portions of other org solvents via idid interactions.

Act as solvents to dissolve water soluble substances eg KOH, KCN and org substances - as it has polar -OH grp and a np hydrocarbon chain

Question 9

Preparation of alcohols (3 main)

Answer 9

Alkenes -------> alcohols
ELECTROPHILIC ADDITION
R&C: 
- Lab method
Step 1: cold conc H2SO4 Step 2: H2O and heat 
OR
- industrial preparation 
H2O(g)/conc H3PO4, 70atm, 300°C 

Halogenoalkanes —–> alcohols
NUCLEOPHILIC ADDITION
R&C: NaOH(aq), heat

Carboxylic acids, aldehydes & ketones ——> alcohol
REDUCTION

carboxylic acid —-> 1° alcohol
LiAlH4 in dry ether

Aldehyde —-> 1° alcohol
LiAlH4 in dry ether OR
NaBH4 OR
H2, Ni, heat

Ketone —-> 2° alcohol
LiAlH4 in dry ether OR
NaBH4 OR
H2, Ni, heat

Question 10

Function of LiAlH4 & NaBH4

Why is dry ether solvent used for reduction using LiAlH4?

Answer 10

Source of hydride ions (H-)

LiAlH4 is such a strong reducing agent that it can react with water
H- + H+ —-> H2

LiAlH4 & NaBH4 do not reduce C=C, but H2, Ni, heat does

Question 11

Reactions of alcohol (5 main) - the flowchart thing

Answer 11

Combustion

Rctns involving fission of C-O bond

• > Substitution of -OH by -X
• dry HX and heat
• PX3
• PCl5
• SOCl2
• > Dehydration/elimination
• excess conc H2SO4, heat
• Al2O3 or H3PO4, heat

Reactions involving fission of O-H bond

• > reaction with Na
• > condensation
• RCOOH, conc. H2SO4, heat/heat under reflux
• RCOCl, rm temp

Oxidation

• > oxidation of 1° ROH to aldehydes
• K2Cr2O7, dilute H2SO4, heat with immediate distillation
• > oxidation of 1° ROH to RCOOH
• K2Cr2O7(aq), H2SO4(aq), heat under reflux
• KMnO4(aq), H2SO4(aq), heat under reflux
• > oxidation of 2° ROH to ketones
• KrCr2O7(aq), H2SO4(aq), heat under reflux
• KMnO4(aq), H2SO4(aq), heat under reflux

Tri-iodomethane rctn
- I2(aq), NaOH(aq), heat

Question 12

Combustion - eqn + colour of flame when…

Answer 12

CH3CH2OH(l) + 3O2(g) –heat–> 2CO2(g) + 3H2O(l)

With a gd supply of air, alcohols burn with a pale blue (non-luminous) flame to give CO2 and water

With a limited supply of air, alcohols burn with a yellow (luminous) flame and some soot is also formed.

Question 13

Halogenation
Name of mechanism? MECHANISM NOT REQUIRED THO
R&C (4)

Answer 13

Nucleophilic substitution

R&C: