1990-03-23 — Page 25

( 25 )商敎 日七廿月二年午庚曆夏

報日僑華

五期星 日三廿月三(〇九九一年九十七國民華中

A

1990 中學會考預習專欄

明 出版社

Chemistry (25)

exidising agents commonly used, are:

(1)acidified KMMO (Chromic acid)

(2)acidified KC207

(3)copper at 250°C

Thermometer

Distilling

flask

Receiver

Mixture P and conc H2SO

e.g. CH2CH2H 201

- CẠNH

Cold wator

Ethanoic acid

ALL & DALF PRESS

Unit 14 (Continued)

3. Summary of chemical properties

R. Chu

Hater-bath

Hoat

Alkanes

1. Preparation By heating sodium alkaneate with soda line.

Hapo "Na"

Sodium alkanoate

KH + No2[

&

Soda lime is a solid mixture of quickling (CaO) and NaOH, .e.g. Cl2onttia + NaOH ----

+

CHCH, Wa2co

Alkanoic acids

1. Preparation By Oxidation of alkanols

fol

Alkanoic acid + 11th

Alk Jun

Oxidising agents used: KMnO2/H* or K2Cr2O7/H*

2.9. CH2CH2CH2OH + 2(0).

Propan-1-01

2. Reactions

(a)As a weak acid

CH2CH2COOH Propanoic acid

+

Alkanoic acids, when dissolved in water, are slightly lonized to give hydronium ions (0) that are responsible for acidic properties.

Alkanoic acid + Haf

Alvanoate inn +

They are

Ethyl propanoate

(a) Give the structural formula of

ethyl propanoate.

(D) Name TWO compounds which are most probably contained in the mixture P.

(c) Write an equation of the formation

of ethyl propanoate.

(d) State

TWO functions concentrated sulphuric

this experiment.

of acid

the

in

(e) Give the name of the apparatus Y in

the diagram.

(f) Which of the two openings, A and B,.

is the water inlet?

(g) (1) What would be obtained

on

heating some ethyl propanoate with sodium hydroxide solution? (2) Write an equation of the

reaction.

(3) What type of reaction is this?

(h) Why is the receive immersed in the

cold water?

2; ReactionS

Alkanes are rather chemically unreactive. Under ordinary conditions, they are inert to arials, basés, reducing or cxidising agents, etc. Ca‡Combustion pursing in air with a slightly ominous flame, giving

te and steam,

Enti+2 (102

caur is formed if oxygen is insufficient.

249, CH4 +20%

20H • 302

CO2 = 2H2?

--- 203 40

CH2 D2C + 2450

(b)Substitution reaction

Aikenes are saturated hydrocarbons, i.e. all their bonds are single bonds. The H-atoms in alkanes can be substituted by halogen atoms

an the presence of sunlight..

Thus, they exhibit many properties typical of acids. momobasic acids.

8.5. (1) CH2COOH + H2# # C#‚¢on" + H20*

(2) 20H,0004 + 19 —— (3) 2CH3COOH + NaCO3

(4) CH-COOH

+ NaOH

• Mg(CH3000); + H2

(Ester formation - a condensation reaction

+

2CH2000 Na + H2 C¿ CH2C00 ̃Na* • H2

*H* catalyst

Alkanoic acid Alkanol

Ester

{fragrant smell}

0

H

denotes alkyl groups.

i.e, &C OH + C

The reaction is reversible.

ORA-C -

+

H2O where A-and-

2.9. CH2COON 4 C250 CH2COOCH

+ H2O

Cthyl ethanoate

(c)with chlorides of phosphorus (PC or PC131

0

Alkane 4

£2

e.q.

Halogens alkanes HX

X: C1, Br,

direct sunlight

explosive reaction.

diffused light

in darkness

smooth reaction

no reaction

CH2 Cz

Thus, light is necessary for the reaction to take place, so, it is photochemical reaction, The reaction between CH, and Cly is given below.

CH2+ Cl2 --- HC1+ CH2C (monochloromethane)

CH2C+012 -- HC1.+

CHC (dichloromethane)

HOT CHC1, (trichloromethane)

--- HCL + 001 (tetrachlorgrethane!

catalyst simpler simpler alkanes alkenes

IN.O. This on Triportant industrial method of obtaining alkenes from

petroleon. I

·C++ 242 {Pyrolys)

(elThermal cracking

large alkanes

1273×

Bit. CH1

스

Alkenes

1. Preparation By debydration of alkano's.

Dehydrating

wering agent

kano

Alkene + H20

Denydrating agents commonly used are:

(alhot, nglazed porcelain (using alkanol vapour),

(b)conc. E2504 excess. at 175 to 180°C).

(c)hut alumina (A!203}])

(diphosphoric acid.

e.g. CC

7. Reactions

conc 150,

ཏཾཏམཱུ ཡིཾཏྟ

(a)Combustion burning with a smoky flame, givingsteam only.

Catan 2007

1

e.g. - City 302

+

+

i

2002 20

(b)Addition converting unsaturated compounds to saturated compounds.

Examples

.8

White Funes of HC11g) are seen and an alkancyl chloride is formed,"

Alkanoic acid PC15

Aikanoy! chloride

+ POCT + HOT

e.g. CH2C-- ON!+ PC1

・CH2C El + HCl

Ethangy)

chloride

共

-no spefic tes

tate the reagents and conditions ssary for each of the following versionS Write an equation of ach convers

4.2 Alkenes

X

(a) Rapid decolourization

of

11. X

broming water Br2/H20) or

iii. X

iv. X

bromine in tetrachloromethane

}.

(d) Write an

equati

between P and bromine interachloromethane,

(b) Rapid decolourization of

acidified

potassium

permanganates (KMnO¡/HT).

4.3 Alkanols

(a) Smell e.g. CH2OH and Cyl2OH. (b) Burning with a blue flame

(c) Forming fruit-smelling ester

with an alkandic acid,

(d) Evolving H2 gas on adding

sodium metal.

4.4 Alkanoic acids

maynes i u

(a) Evolving H2 gas on adding to the aqueous solution of the acid. (b). Forming fruit-smelling

with an alkanol.

ONG KONG

(1)With halogens,} - rapid decolourization, forming sly drops.

CH2 = CH2 + X2

(2) With hydrogen halides (HX)

CH2

+ 4X

(3)Catalytic hydrogenation

CH2 = CH2+ H2

(4)With cone. 11,50

X: 01, Br, I.

CH2 CH2X

Mi o. F

CH-CH3

A

CHCHHSO4

180°C

لالالالالالالا

CHCHHS +120 CH2CH2O + H250

ic)oxidation

J

Acidified KM is decoleurized by alkenes, CH = CH2 + iD) + HD

(d)Polymerization

www.

CH2CH2OH

ethane-1, 2-dicl

Since an alkent molecule consists of carbon-carbon double bond, so, under high temperature and pressure it can join to one another to form eng uhatus of polymer by addition reaction.

a little 2 as catalyst

9- CH2 C2 heat, high pressure

e.g.

CH2=CH2+ H2SO2

Alkanois

1. Preparation

(a)By hydration of alkanes

City CH2 - HSO4 + H2SO

(b)By fermentation of sugar to give ethanol

+ CH2- CH2+

polythene

CHZE2- LESD

+

·Sugar

Yeast Hydrolysis glucose

Ethano! + £2

+ energy

Enzymes

or

26°C - 36°C

fructase

2. Reactions

(a)Combustion

CO

2002 + 3420

··

e.g. 25 30,

tb with very reactive metals (eg. K, Nal-tydrogen gas is liberated

and alkanols act as weak acids.

Alkanol Na

·Sodiya

alkoxide

e.g. C2H2CH N2 →→→

+

sodiun

(c)with chlorides of phosphorus (PC) and PC15)

White misty fumes of HCI (g) are seen and a chloroalkane. is obtained.

e.g. Callech + 2015

→

POCI, HCF

CHEC chloroethene (d)Dehydration-converting alkanels to alkenes

Alkanol Dehydrating agent. Alkene + 10

e.g. C2Hi

(e)Oxidation

∙CH2

CH,

180°C

10)

(0)

Alkanol

· Alkanal ———— Alkanoic acid

Uses

Alkanes

a) as us. (b) asorgant

solv

(c) as grease oils,

Question 14.2

An organic liquid-X has the-structural formula as shown below.

CH3

X: CH3CH CH2

ester

(a) Name the compound X the IUPAC systems

Fding to

(b) There

isomeric

FBR

other compounds and having many properties filar to X. Write out their structural formulae and name them according to the: - TUPAC

IC

(d) as a source of raw materials of

plastics.

5.2 Alkenes

As raw materials of many plastics, e.g. ethene for making polyethene..

5.3 Alkanols

(a) Ethanol in alcoholic drinks. (b) As organic solvents, e.g. CH2OH

for points and dyes; C2H5OH for cosmetics and perfumes, etc. (c) As fuels in spirit lamps. (d) In manufacture of synthetic fibres, ethanoic acid and esters.

5.4 Alkanoic acids

(1) Ethanoic acid in vinegar. (2) In manufacture of esters, dyes,

artificial silk, drugs, etc. (3) Congulation of rubber latex.

Question 14.1

A simple alkanol X has a molecular Formula C3Hg. On suitable treatments X. can be converted separately to compounds P, Q, R and S in one step. P, Q and R contain the same number of carbon atoms as X.

P

ง

X

(C51002)

A Chloroalkane

R

P can decolourize bromine solution in tetrachloromethane.

Q can turn a wet pli paper. red.

S is a sweet-smelling liquid, insoluble in water.

Q

(a) State the names of the homologous

series to which

and P respectively belong.

(b) Identify and name, according to the IUPAC systems; the compounds X, P. Q, R and S.

systems.

(c) Describe what would you observe and write an appropriate equation of the reaction on adding the following Substances separately into. X.

1. A small piece of sodium metal. ii. A few drops of phosphorus (v)

chloride.

(d) In the experiment as shown below, compound X is vapourized and passed over some hot broken porcelain. A colourless gas Y is formed and passed separately into the bromine. water and the acidified potassium permanganate solution by means of a 3-way tap.

Broken porcelain.

Gas Y

Hoar

Cotton soaked

with liquid X

Bromine water

3-way top

1. (1) What is gas. Y?

Acidified KRO

(2) Write an equation of its

formation.

11. What 15 the function of the

broken porcelain?

iii. (1) What happens to the bromine

water?

(2) What type of reaction is

this?

(3) Write an equation of the

reaction?

iv. (1) What.

happens to the potassium

acidified permanganate?

(2) What type of reaction is

this?

Question 14.3

In the experiment below a mixture P and a little of concentrated sulphuric acid After was refluxed using a waterbath. some while, ethyl propanoate, a sweet- smelling liquid collected in the receiver.

Solution to Q.14.1

(a) P is an alkene.

Q is an alkanoic acid. (b) X is propan-1-ol (CH2CH2CH2OH)

fit could not be propan-2-01 because this compound would not be oxidized to an acid having the same

number of carbon atoms.).

P is propene.

Qis propanoic acid.

R is 1-chloropropane.

S is ethyl ethanoate.

(c) i. Excess conc H250/Heat to 180°C.

CH2CH CH2OH

CH3CH CH2+ #2D

ii. Acidified KMnO/Heat.

CH3CH2CH2OH

+ 2(0)

CH3CH2COOH + H2O

ii. PCI/No heating required.

∙CH2CHCHH + PCT.

CH3CH2CH2C) + POCT 3 + HCT.

iv. Ethanoic acid (CH,COOH), conc

H2SO/Heat.

→

CHCH CH2OH CH2COOH - CH3COOCHCH2CH3 + H2

(b) CH2CH = CH2+ Br2

Solution to Q.14.2

CH2CHBrCH2Br

(a) X is 2-methylpropan-1-01. (b) CH2CH2CH2CH2DH

Butan-1-ol CH3CH2CHCH3

OH

Butan-2-ol

CH3.

2-methylpropan-2-01

(c) i. Effervescence occurs as

given off.

2(CH3)2CHCH2OH

+ 2Na

2(CH2)2CH2 CH20 ̃Na + H2

is

ii. White fumes. hydrogen chloride

(d) i.

are seen.

(CH3)2CHCH2OH + PC15

(CH3)2CHCH2C1 + POCT 3 + HCT

(1) Y is 2-methylpropene. (2) (CH3)2CHCH2ON

(CH3)2CH CH2 + H2O

ii. It dehydrates the alkanol X.

iii. (1) Bromine

water

is

decalourized. (2) It is an addition reaction. (3) (CH3)2CH = CH2+ Br2

(CH3)2CHBr CH2Br

iv. (1) The

solution

decolourized.

(2) IL is an oxidation,

Solution to 0.14.3

is

(a) The structural formula of ethyl

propanoate is CH3CH2CH2CH3.

(5) The two compounds are propanoic

acid and ethanol.

(c) CH3CH2COOH + CH2CH2OM ~

CH2 CH2 COOCH 2 CH2 + H2D

(d) Conic H2SO, acts as a catalyst and a

dehydrating agent.

(c) Y is the Liebig condenser. (f) B is the water inlet..

(g) i. Sodium propanoate and ethanol

are obtained. ii. It is the alkaline hydrolysis

of ester.

111. CH2CH2COOCH2CH3 + Nanн

CHỊCH, CON NÓN CHO CHO H

(h) This is to reduce the vapourization

of liquid ethyl propanoate.

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