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Hydroxy Compounds + Aldehydes Flashcards

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1
Q

thiols: RSH

bp of alcohol compared to thiols and alkanes

A

Much higher. More energy required to overcome strong H bonding between OH molecules compared to weaker pd-pd between thiol molecules and id-id between alkane molecules.

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2
Q

What affects bp in alcohols?

A
  1. no. of electrons (polarisability –> strength of id-id)
  2. Degree of branching (surface area for id-id)

greater degree of branching = more spherical molecule

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3
Q

solubility of OH compared to alkane (in water)

A

More soluble as it can form H bonds

Energy released from formation of H bonds is sufficient to overcome energy absorbed from the breaking of id-id between RH molecules and H bond btwn OH molecules

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4
Q

Solubility of alcohol as size increases

more C in molecule

A

Hydrophobic nature increases with increasing no. of C –> solubility decreases

Since extent of H bonding decreases

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5
Q

Is alcohol acidic, neutral or basic in water?

A

aq OH is neutral

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6
Q

Why is alcohol a weaker acid than water?

A

Destabalisation alkoxide anion by charge intensification because R group exerts stronger e donating I effect than H. RO- formed less easily; POE lies more to left

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7
Q

Acid strength of alcohol as size increases

A

decreases

bigger R = larger e donating I effect = further intensify -charge on RO-

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8
Q

Hydration of alkene

form OH

A

conc. H2SO4, heat with water (l)

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9
Q

NS of RX to give OH

A

NaOH/KOH (aq), heat

alcoholic medium for this one favours elimination of HX

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10
Q

Form OH from COOH

A

Reduction
LiAlH4 in dry ether

Why carboxylic acid cannot be reduced by anything else? Is it cos of strength of reducing agent? Yes

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11
Q

Form OH from aldehyde or ketone

A

LiAlH4 in dry ether
OR NaBH4 in methanol or aq
H2, Pt/Pa catalyst
OR H2, Ni catalyst, heat

aldehyde –> pri alc
ketone–> sec alc

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12
Q

Why must LiAlH4 be in dry ether but NaBH4 can be aq or alc?

A

LiAlH4 is highly soluble in ether, but reacts violently with water to produce H2 gas, so we want to maintain a dry and inert environment as much as possible.

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13
Q

NS of OH to give RX

A

HX (g), heat
OR PX3, heat
OR PCl5
OR SOCl2, heat

*for HCl, heat, need to add ZnCl2 catalyst because of strong H-Cl bond

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14
Q

Does alcohol react with Na? NaOH? Na2CO3?

A

Only reacts with Na because it is a weak acid.

Na (S)

Acid base reaction, form H2 gas

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15
Q

Oxidation of alcohol to carbonyls and carboxylic acids

Conditions + Products

A

Pri:
1. K2Cr2O7, heat and distill (Aldehyde)
2. K2Cr2O7, heat OR KMnO4, heat (COOH)

Sec:
K2Cr2O7, heat OR KMnO4, heat (ketone)

Tertiary no reaction because no hydrogen atoms on C with OH group

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16
Q

When can we not use KMnO4 to oxidise? Why?

A

Methanol and ethanol. Oxidised to CO2 instead of carboxylic acid.

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17
Q

Dehydration of alcohol

A

excess conc. H2SO4, heat

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18
Q

Condensation to ester from OH

A

Alcohol + COOH
Conc H2SO4 catalyst, heat

Alcohol + RCl
rtp

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19
Q

Naming of ester

A

CH3CO2(CH2)3CH3
Butyl ethanoate

Name of alcohol THEN name of COOH

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20
Q

Tri-iodomethane (iodoform) formation + equations

A

(CH3)CR(H)(OH)/RCOCH3 group present
I2, NaOH (aq), heat

Form CHI3, pale yellow ppt with antiseptic smell

Negative test for COOH, R-Cl and COO groups

RCH3CHOH + 4I2 + 6OH- -heat-> RCOO-Na+ + CHI3 + 5NaI + 5H2O
RCOCH3 + 3I2 + 4NaOH -heat-> CHI3 + 3NaI + 3H2O + RCOO-Na+

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21
Q

What type of reaction is iodoform formation? Write out balanced equations.

Study These Flashcards
A

Oxidative cleavage.
1. RCH3CHOH + I2 + 2NaOH –> 2H2O + RCOCH3 + 2NaI (oxidation)
2. RCOCH3 + 3I2 + 3NaOH –> RCOCI3 + 3H2O + 3NaI (stepwise sub of H in CH3 with I)
3. RCOCI3 + NaOH –> RCOO-Na+ + CHI3 (cleavage)

22
Q

Phenol physical properties

Study These Flashcards
A

Colorless, hygroscopic (absorbs moisture from the air)
May contain a tint due to oxidation products
Corrosive, powerful antiseptic

23
Q

Boiling point of phenol (vs alcohol)

Study These Flashcards
A

High because of H bonding between molecules

Higher than alcohol due to delocalisation of LP of O into benene ring (p orbital of O and C overlap)–> interactions stronger (O more “electronegative”)

24
Q

Solubility of phenol

Study These Flashcards
A

Relatively soluble in water (below 68.5 degrees celcius = relatively; above = fully soluble)

25
Acidity of phenol vs alchohol vs water
phenol>water>alcohol | stability of --xide = more willing to stay as anion + H+ = more acidic ## Footnote P orbital of O overlap with P orbital of C in benzene ring --> delocalisation of negative charge on O into benzene ring --> phenoxide anion stabalised by charge dispersal --> more acidic than water (no delocalisation effect) --> POE shift right R group in alcohol exerts e donating I effect --> intensify - charge on OH- --> alkoxide ion less stable than hydroxide --> POE more left --> weaker acid
26
Does phenol react with Na? NaOH? Na2CO3?
Not with Na2CO3. Phenol is a weaker acid than carboxylic acid --> not acidic enough to release CO2
27
Does phenol undergo elimination or dehydration? Why?
No. LP delocalisation into benzene ring = partial double bond on C-O = cleavage of CO doesn't really happen (if at all).
27
Strength of nucleophile: Phenol vs Alcohol
Phenol weaker Nu because p orbital of oxygen overlaps with P orbital of C in benzene ring --> delocalsation of LP--> less available for donation
28
Condensation of phenol (esterification)
Conditions: NaOH (aq) Only reacts with acyl chlorides not COOH; alkali gives stronger nu to react with COCl
29
Phenol or benzene more reactive? Why? | So how does this affect reactions and conditions of reactions?
Hydroxy group strongly activating since it enhances electron density in the ring (resonance effect), making phenol much more susceptible to electrophilic attack. So reactions of phenol can be conducted under milder reactions and conditions.
30
Nitration of phenol
Monosub: Dilute HNO3/HNO3 (aq) Tri-sub: Conc HNO3
31
Halogenation of phenol + observations (if any)
Monosub: Br2/Cl2 in CCl4 Polysubsitution w/o catalyst: Br2/Cl2 (aq) Orange (- red) Br2 decolourised and white ppt formed
32
Ferric Chloride test
FeCl3 (aq) Forms a purple/violet colouration | Distinguishing test for Phenol
33
How to name ketone and aldehyde?
Ketone: remove e, replace with -one Aldehyde: remove e, replace with -al
34
bp of carbonyls compared to alkanes
Higher. moderately polar since electronegative O--> permenant delta positive on C --> has pd-pd
34
solubility of carbonyls compared to alkanes
Soluble in polar and non-polar solutes. Solubility decreases as Mr increases since extent of H bonds decreases --> less energy released --> harder to overcome H bond | energy released from formation of bonds, absorbed during breaking
34
Similarity between alkenes and carbonyls in terms of reaction they undergo
Both unsaturated = undergo addition reactions
35
Step up reaction for carbonyls
HCN (aq) with trace NaCN (aq)/(s) as catalyst OR HCN (aq) with NaOH (aq)
35
Diff in reactivity of alkenes and carbonyls towards nu reagents
C=C non-polar; C=O polar. electron deficient carbonyl C makes it susceptible to nu attack, but electron rich alkene C disfavours nu approach
36
Explain NA mechanism for step up of carbonyls
HCN weak acid, partially dissociates to give CN- (nu). Base neutralises HCN to give water soluble salt which dissociates to give nucleophile, CN-. Alternatively, NaCN added as catalyst to increase amt of CN- present. CN regarded as catalyst since it is regenerated at the end of reaction
36
If reaction of carbonyl with HCN forms a chiral product, will it be optically active? Rate equation?
No, racemix mixture formed Rate equation = k[carbonyl][CN-]
36
Draw reaction mechanism of HCN NA with CORR'
*Check phone photo*
37
Reactivity of ketone vs aldehydes to nu
1. electronic factor: Ketone alpha C less electron-deficient since 2 e donating alkyl groups 2. steric hinderance: alkyl bulkier than H
38
Hydrolysis of nitrile
Acid hydrolysis (H2SO4 (aq), heat) Base hydrolysis (NaOH (aq), heat)
39
Reduction of nitrile
Product: Primary amide LiAlH4 in dry ether OR H2, Ni Catalyst, heat OR H2, Pd/Pt Catalyst
39
Carbonyl with organic derivitives of ammonia
-C=O + H2N --> -C=N- + H2O (R1R2C=NNH2- hydrazone) Forms Hydrazine, Phenylhydrazine and 2,4DNPH
39
Silver mirror test
Tollen's reagent (Ag(NH3)2)+, heat Works for all aldehydes. Forms silver mirror | RCHO + 2(Ag(NH3)2)+ + 3OH- -heat-> RCOO- + 4NH3+ 2Ag + 2H2O
40
Test for carbonyl compounds
2,4 - DNPH product: orange ppt with sharp characteristic mp
40
reduction of aldehyde and ketone to OH
aldehyde --> pri OH ketone --> sec OH LiAlH4 in dry ether OR NaBH4 in methanol/aq OR H2, Ni Catalyst, heat OR H2, Pd/Pt Catalyst
41
What mechanism does reduction of carbonyls follow + why LiAlH4 and NaBH4 cannot react with alkene.
Nucleophilic attack (because carbonyls can have delta positive regions due to electronegativity diff but Alkenes cannot) C=C is electron rich, there are no electron deficient areas for Al/B to attack + electrons on C=C also repel the approach of the negatively charged Al-/B-, so no reduction by either of them.
42
Distinguishing tests: aldehyde vs ketone
Aldehyde reduced, ketone cannot 1. K2Cr2O7 (aq), H2SO4 (aq), heat OR KMnO4 (aq), H2SO4 (aq), heat Orange to green Purple to colourless 2. Tollen’s reagent (silver mirror test) 2Ag(NH3)2+ + 2OH- + R1R2CO -heat-> 4NH3 + 2Ag + 2H2O + R1R2CO- 3. Fehling’s reagent (brick red ppt formation) (only positive test for aliphatic not aromatic) 2Cu2+ + 5OH- + R1R2CO -heat-> Cu2O + 3H2O + R1R2CO-
43
Fehling's solution
Fehling's solution, heat Only works for aliphatic aldehydes. Forms brick-red ppt | RCHO + 2Cu2+ + 5OH- -heat-> RCOO- + Cu2O + 3H2O

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