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Chemistry A-Level OCR > Carbonyls And Carboxylic Acids Chp26 > Flashcards

Carbonyls And Carboxylic Acids Chp26 Flashcards

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1
Q

What is the difference between carbonyl compound and alkenes?

A

The C=C double bond in alkenes are non polar where’s C=O double bond in carbonyl compounds is polar. Due to the polarity, aldehydes and ketone react with some nucleophiles (nucleophilic addition)

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2
Q

Why are carbonyls stronger than alkanes?

A

Carbonyls have permanent dipole-dipole interactions which are stronger compared to alkanes which use London forces which are weaker.

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3
Q

Aldehydes and Ketones Solubility in water

A

Aldehydes and ketones mix completely in water because the hydrogen bonds form between the oxygen of the carbonyl compounds

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4
Q

What are the four nucleophiles that are used nucleophilic addition?

A

:-OH, N:H3, H2:O, :-CN

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5
Q

What are the reagent and conditions used for the reaction with HCN?

A

Reagent- H2SO4/NaCN

Conditions- Reflux in acidic solution

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6
Q

What are the dangers of HCN?

A

Hydrogen cyanide is a highly volatile liquid which has a faint bitter almond smell and toxic.

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7
Q

What are safer alternatives for HCN?

A

KCN + H2SO4
NaCN + H2SO4
Which are solid at room temperature and easier to handle

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8
Q

What are the reagents, nucleophiles and products of reduction with NaBH4?

A

Reagent: NaBH4 (reducing agent)
Nucleophile: H- (aq) (hydride ion)
Products: Primary alcohols (aldehydes) and secondary alcohols (ketones)

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9
Q

Why can’t H- act as an electrophile?

A

H- cannot act a partially positive so it cannot as an electrophile

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10
Q

What reagent is used to identify the presence of carbonyl compounds?

A

Brady’s reagent / 2,4-DNP

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11
Q

Observation for a positive result for Brady’s/ 2,4-DNP

A

Yellow or Orange precipitate

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12
Q

Why can solid 2,4 DNP be hazardous?

A

Solid 2,4- DNP can be very hazardous because friction can cause it to explode.

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13
Q

What type of reaction is the test for for detecting carbonyl compounds?

A

Nucleophile addition elimination and condensation reaction.

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14
Q

What is the reagent used to distinguish between aldehydes and ketone?

A

Tollens’ reagent (ammoniacal silver nitrate solution)

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15
Q

What are the observations/ positive results for tollens reagent

A

Silver mirror is produced if an aldehyde is present

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16
Q

What practical method is used for tollens’ reagent?

A

Heat unknown solution in water bath as you add tollens reagent.

17
Q

What type of reaction is present when tollens reagent is used and what is the equation?

A

-Oxidation reaction
- Aldehyde + [O] —> carboxylic acid
- Ag+ (aq) + e- —-> Ag(s) (silver mirror)

18
Q

What are melting point apparatus used to identify?

A

Identify a specific aldehyde or ketone

19
Q

Practical method for melting apparatus to identify carbonyl compounds

A

-Filter the solution under reduced pressure
- Recrystallise it
- Use melting point apparatus to determine the melting point (capillary tube and thermometer)
- Compare the melting point to a database

(A physical change)

20
Q

Why does CA have a high melting point?

A

-Forms hydrogen bonds so high melting point and CA with up to 4 carbon atoms are soluble in water

21
Q

What happens to the solubility as the chain increases?

A

As chain increases, the solubility will decrease as the non-polar chain has a greater effect on the overall polarity of the molecule.

22
Q

CA reaction with metals

A

Type of reaction: Redox

Description and products; H2(g) + carboxylate salt - Effervesence as H2 gas and metal dissapears

Equation: 2CH3CH2COOH(aq) + Mg(s) -> (CH3CH2COO-) Mg2+(aq) + H2

23
Q

CA reaction with metal oxides

A

Reaction: Neutralisation

Description and products: Salt + Water

Equation: 2CH3COOH(aq) + CaO -> 2(CH3COO-)Ca2+ (aq) + H2O

24
Q

CA reaction with alkalis

A

Reaction: Neutralisation

Description and products: Salt + Water

Equation: CH3COOH(aq) + NaOH(aq) -> CH3COO-Na+(aq) + H2O(l)

25
Q

CA Reaction with carbonates

A

Reaction: Neutralisation

Description and products: Salt + Water + CO2 - effervescence bubbles and solid carbonate will disappear

Equation: 2CH3COOH(aq) + Na2CO3(aq) -> 2CH3COO-Na+ (aq) + H2O + CO2 (g)

26
Q

Test for carboxylic acids

A

Only CA can react with carbonates as they are sufficiently acidic (it can react with weak bases), this how you distinguish it from a phenol

Chemistry A-Level OCR (34 decks)

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