Carbonyl compounds Flashcards Preview

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Flashcards in Carbonyl compounds Deck (34):
0

Aldehyde

-CHO
eg butenAL

1

Ketone

-COC-
eg. ButanONE

2

Alkyl

Alkane with H atom removed

3

Aryl

Cyclic compound containing benzene ring

4

Why is carbonyl group polar?

C=O bond polar due to electronegativity on oxygen atom - more electrons in bond (Pi and sigma) towards O atom

5

Why is C=O soluble in water?

Polar so smaller aldehydes and ketones are soluble in water - form H bonds (up to 4 carbons in the chain)

6

Why do ketones and aldehydes has higher boiling points than alkanes?

Permanent dipole-dipole forces between molecules

7

What is the oxidising agent used in the oxidation of alcohols and aldehydes?

[O] = Potassium dichromate (VI) with sulfuric acid or acidified potassium dichromate (Cr3O72-) which is orange and goes to green Cr3+

8

Conditions for primary alcohol ➡️ Aldehyde and ?

Heat gently and distill using oxidising agent
Forms 1 molecule of water too

9

Conditions for oxidisation of ketone to carboxylic acid and ?

Heat under reflux with excess H2SO4 and oxidising agent
1 molecule of water also forms

Cannot be oxidising further

10

Condistions for secondary alcohol ➡️ ketone

Heat gently using oxidising agent
Forms 1 molecule of water too

Cannot be oxidised further and tertiary alcohols cannot be oxidised at all

11

Reducing agent for reduction of carbonyl compounds

2[R] = ️sodium tetrahydridborate (III), NaBH4, which is a source of H-

12

Conditions for reduction of aldehydes ➡️ primary alcohols and ketones ➡️ secondary alcohols

Warm using reducing agent and water as the solvent

13

Mechanism for reduction of carbonyl compounds

Nucleophilic addition
1) nucleophilic attack H- with lone pair to Cdelta+ and pair of electrons from Pi bond to Odelta-
2) adding water - lone pair on O- goes to H atom on water and pair of electrons in H-O bond goes to the O
Forms an alcohol and OH- molecule

14

Brady's reagent test

2,4-dinitrophenylhydrazine
Addiction across a double bond and elimination of water means ghat a C=O bond is present
Forms a yellow/orange precipitate with only aldehydes and ketones
To find specific ketone or aldehyde, the mpt of the crystals formed can be compared with a database

15

Silver mirror test

Tollens' reagent - ammonical silver nitrate [Ag(NH3)2]+
Add tollens' reagent and warm gently in a water bath
A silver mirror forms on the side of the test tube from a colourless solution with aldehydes only
The aldehyde is oxidised and Ag+ reduced
No silver mirror with ketones as cannot be oxidised further

16

Carboxylic acids

-COOH

17

Why do carboxylic acids partially dissociate?

Weak acids

18

Why are carboxylic acids soluble in water?

Highly polar - C=O and O-H
Form H bonds - 2 per molecule
Only soluble up to 4 C in chain length as longer chain non-polar

19

Carboxylic acid + metal ➡️

Metal salt + H2

20

Carboxylic acid + carbonate

Metal salt + CO2 + H2O

21

Carboxylic acid + base ➡️

metal salt + water

22

Esters

-COOC
From carboxylic acid and alcohol
Name alcohol then acid eg ethyl propanoate

23

Formation with carboxylic acid and alcohol

With conc H2SO4 catalyst
Goes to ester and water

24

Formation from acid anhydride and alcohol

Acid anhydride - 2 carboxylic acids with water molecule removed
React with alcohol - forms ester (usual naming - alcohol then acid) and a carboxylic acid
Forms a better yield of ester as not reversible

25

Uses of esters

Perfumes
Food flavourings
Oils

26

Acid hydrolysis of esters

Reflux ester with dilute H2SO4 or HCl
Ester + water (reversible) ➡️ carboxylic acid and alcohol

27

Alkali hydrolysis of esters

Reflux with alkali eg NaOH
Ester + NaOH ➡️ metal salt + alcohol

28

What is a triglyceride?

- a triester of propane-1,2,3-triol (glycerol) and a fatty acid (octadecanoic or hexadecanoic acid). All 3 alcohol groups esterified

29

What does C18,1(9) mean?

18 carbons, 1 double bond on the 9th carbon of a fatty acid (carboxylic acid)
There are trans and cis versions of this

30

Why are saturated and trans fatty acids worse for health?

Pack together more closely a solid and block arteries leading to CHD and increased heart attack risk
Contain bad LDL cholesterol which sticks to artery walls and plaque builds up

31

Why are monounsaturated and polyunsaturated fatty acids better for health?

Contain good HLD (high lipo-density) cholesterol which carries bad cholesterol away from arteries so lower blood pressure and lower risk of CHD

32

What is biodiesel made from?

Vegetable oil or animal fat - long chain alkyl esters
Triglyceride + 3H3OH (reversible + NaOH) ➡️ 3H3C-O-C=O + glycerol

33

What is biodiesel used in and what are the issues?

Used in standard Diesel engines or blended with petrodiesel
Carbon neutral: same amount of CO2 absorbed when growing as is released when burned as a fuel
But may lead to increase in food prices and starvation