Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

La Chimie H2 > Composés carbonyles > Flashcards

Composés carbonyles Flashcards

1
Q

Give general formula for saturated aliphatic carbonyl compounds

A

Aldehyde: CnH2n+1CHO

Ketone: CnH2n+2CO

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is one big difference between aldehyde and ketone?

A
  • Aldehyde hv carbonyl group at end of chain
  • Ketone hv carbonyl group in non-terminal posit n in chain

*NOTE: carbonyl group refers to C=O, not the same as carbonyl compounds!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe nomenclature of aldehydes and ketones

A

aldehyde:
- -CHO carbon is numbered carbon 1
- name ends in -al (eg propanal)

ketone:
- parent chain is longest one containing ketone group
- numbering begins at end nearer carbonyl carbon (if needed, number indicates pos n of carbonyl group in chain)
- name ends in -one (eg butanone)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the difference between aromatic and aliphatic ketone/aldehyde

A
  • aromatic: -CHO/-C=O grp directly attached to a benzene ring
  • aliphatic: -CHO/-C=O grp NOT directly attached to a benzene ring (attached to alkyl grp)

NOTE: if alkyl grp also hv benzene ring somewhere, compound considered aromatic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Explain boiling points of carbonyl compounds

A
  • polar molecules bcos large diff in electro-vity btw C & O, so C=O bond is polar
  • (more than alkane of comparable Mr) More energy needed overcome stronger pd-pd attract n btw aldehyde/ketone molecules vs weaker id-id attract n btw non-polar alkane molecules
  • (less than alcohol of similar Mr) More energy needed overcome stronger H bonds btw alcohol molecules vs weaker pd-pd attract n btw aldehyde/ketone molecules

NOTE: aldehyde and ketone cnt form H bonds w itself bcos H not covalently bonded to O, so cnt form H bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Explain solubility of carbonyl compounds in water

A
  1. Lower aldehyde, ketones (eg methanal, ethanal, propanone) r completely miscible in water (no separate layers
    bcos
    - energy released by form n H bonds btw aldehyde/ketone & water molecules enough overcome intermolecular H bond btw water molecules & pd-pd attract n btw aldehyde/ketone molecules

NOTE: aldehyde/ketone cnt form H bond w itself but can form H bond w water molecules

  1. Solubility of aldehydes/ketones in water decrease for higher aldehyde/ketone members (more C)
    bcos
    - larger non-polar R grp make molecule more hydrophobic
    - main interact n btw larger aldehyde/ketone molcules bcome id-id instead
    - energy released fr id-id attract n btw aldehyde/ketone & water molecules insufficient overcome intermolecular H bond btw water molecules & pd-pd attract n (& id-id attract n ) btw aldehyde/ketone molecules
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Carbonyl compounds are formed by …

A

oxidat n of alcohols

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Name reagent, conditions, observation and type of reaction of preparing aldehydes from primary alcohols

A

R&C: K2Cr2O7(aq), H2SO4(aq), heat WITH immediate distillat n
Observ n: orange K2Cr2O7 sol n turn green
Type: oxidat n

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Name reagent, conditions, observation and type of reaction of preparing ketones from secondary alcohols

A

R&C: K2Cr2O7(aq)/KMnO4(aq), H2SO4(aq), heat
Observ n: Orange K2Cr2O7 sol n turn green/ Decolour n of purple KMnO4 sol n
Type: oxidat n

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What reaction do carbonyl compounds undergo in general?

A

Nu Add n

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Explain how susceptible to nucleophilic attack are carbonyl compounds and alkenes

A

Carbonyl cpd
- e-deficient, bcos bonded to electro-ve O atom
- more susceptible to nucleophilic attack

Alkene
- C=C is e-rich
- not susceptible to nucleophilic attack

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Name reagent, condition, type of reaction and application of carbonyl cpd + HCN

A

R&C: HCN w trace amt NaCN (or NaOH) as catalyst, cold
type: Nu add n
Applicat n: increase no of C atom (resulting nitrile can b hydrolysed form RCOOH or reduced to amine)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe a general nucleophilic addition mechanism

A

Step 1: Nu, CN-, attack e- deficient carbonyl C atom, form tetrahedral anion intermediate (C=O bond w dipoles, full arrow fr bond to O) (SLOW)

Step 2: protonat n of intermediate to form stable add n pdt (lp e- fr O attack H fr HCN, full arrow fr H-C bond to CN)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why carbon atom attacks carbonyl compound instead of nitrogen in CN-?

A

bcos
- C less electro-ve
- lp on C can b donated more readily form dative bond to carbonyl grp
- C is btr Nu

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the role of NaOH/NaCN as reagent in nucleophilic addition?

A
  1. NaOH
    - trace NaOH neutralise H+ (fr HCN), decrease [H+]
    - By LCP, eqm pos n shift to increase [H+], so increase in [CN-] & rate of rxn
    - said to b base-catalysed
  2. NaCN
    - soluble, fully dissociates produce initial CN- for Nu attack on e- deficient carbonyl C
    - homogenous catalyst (CN- is regenerated in second step)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What mixture is formed when chiral C is obtained from nucleophilic addition? Why?

A

racemic mix
bcos
- equal probability CN- Nu attack trig planar sp2 hybridised e- deficient carbonyl C atom fr top & bottom of plane
=> form equal amt (+) & (-) enantiomers, thus racemic mix

17
Q

Explain relative reactivity between aldehydes and ketones

A

aldehyde generally more reactive than ketone in Nu add n bcos

  1. steric effect
    - 2R grp in ketone cause greater steric hindrance vs aldehydes w oni 1 grp
    - more difficult for Nu to attack e- deficient carbonyl C in Nu add n rxn
  2. Electronic effect
    - ketone hv 2 e- donating alkyl/R grp, makes carbonyl C less e- deficient/e-philic
    => less susceptible to Nu attack vs aldehyde w oni 1 grp
18
Q

Name reagent, condition and type of reaction of hydroxynitrile to hydroxyamine

A

R&C:
- LiAlH4 in dry ether
OR
- H2 w Pd/Pt catalyst
OR
- H2 w Ni catalyst, heat

type: reduct n

19
Q

Name reagent, condition and type of reaction of hydroxynitrile to RCOOH

A

R&C: HCl (aq)/H2SO4 (aq), heat under reflux
type: acidic hydrolysis

20
Q

Name reagent, condition and type of reaction of hydroxynitrile to RCOO-

A

R&C: NaOH (aq), KOH(aq), heat under reflux
type: basic hydrolysis

21
Q

Describe oxidation reaction of carbonyl compounds

A

only aldehyde undergo oxidation give RCOOH
ketones DON’T

22
Q

Name reagent, condition, observation and type of reaction of aldehyde to RCOOH

A

R&C:
- K2Cr2O7(aq), H+, heat
OR
- KMnO4 (aq), H+, heat
Observ n:
orange K2Cr2O7 sol n turn green
OR
decolourisat n purple KMnO4 sol n
type: oxidat n

23
Q

Describe reduction reaction of carbonyl compounds

A
  • aldehydes reduce to form primary alcohol
  • ketone reduce to form secondary alcohol
24
Q

Name reagent, condition and type of reaction of carbonyl compound to alcohol

A

R&C:
LiAlH4 in dry ether
OR
NaBH4 in ethanol
OR
H2 w Pd/Pt catalyst
OR
H2 w Ni catalyst, heat
type: reduct n

NOTE: NaBH4 can oni reduce carbonyl compounds! (not RCOOH, alkenes, etc.)

25
Q

Why is LiAlH4 a stronger reducing agent than NaBH4?

A
  • bcos weaker Al-H bond vs B-H bobnd, so easier to break produce H- nucleophile (due to extent of orbital overlap)
  • bcos low electro-vity of Al vs B -> shift e- density to H more, make it btr donor of e-
26
Q

Carbonyl compounds can be reduced to alcohols using LiAlH4. But, alkenes cannot be reduced by LiAlH4. Why?

A
  • alkene no hv e- deficient C atom attracting Nu
  • alkene contain C=C w e- rich π e- cloud, repels any Nu fr LiAlH4
  • so, alkene not susceptible to Nu attack by H- fr LiAlH4
27
Q

Define condensation reaction

A

rxn in which 2 molecules added, accompanied by eliminat n of small molecules eg H2O, NH3, etc.

28
Q

Name applicat n, test, observ n & type of rxn of carbonyl cpd + 2,4-DNPH

A

applicat n: chemical test for BOTH aldehydes & ketones

test: add 2,4-DNPH, heat

observ n: orange crystals of 2,4-dinitrophenylhydrazone formed

type: condensat n

29
Q

Name applicat n, test, observ n & type of rxn of carbonyl cpd + tollens’ reagent

A

applicat n: chemical test for aromatic & aliphatic aldehydes (distinguish fr ketones)

test: add Tollens’ reagent (aq NH3 w AgNO3), heat

observ n: for aldehyde, silver mirror/black ppt formed

type: mild oxidat n

NOTE: mol ratio RCHO(aq) = 2Ag(s)

30
Q

Name applicat n, test, observ n & type of rxn of carbonyl cpd + Fehling’s reagent

A

applicat n: chemical test for aliphatic aldehyde ONLY (distinguish fr aromatic aldehyde)

test: add Fehling’s reagent, heat

observ n: brick red ppt Cu2O formed in presence of aliphatic aldehyde

type: mild oxidat n

NOTE: mol ratio RCHO(aq) = Cu2O (s)

31
Q

Name applicat n, test, observ n & type of rxn of carbonyl cpd + I2

A

(iodoform test)
applicat n: identifies aldehydes, ketones w structure CH3 C=O R
where R = H, alkyl, aryl (for aldehydes, only ethanal possible) AND alcohols w structure CH3 CH(OH) R

test: add I2 in NaOH (aq), heat

observ n: pale yellow ppt of CHI3 observed

type: oxidat n

NOTE:
1. carboxylate salt pdt hv 1 less C atom than reactant
2. carbonyl cpd w CH2ICO-, CHI2CO-, CI3CO- grp oso register +ve test
3. iodoform test CANNOT test for carbox acid, acyl chloride, esters
4. mol ratio R C=O CH3 = CHI3

La Chimie H2 (25 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions