other organic chemistry

Question 1

explain what is meant by fractional distillation

Answer 1

separation of compounds by their boiling points

Question 2

nowadays used catalyst in cracking

what kind of catalyst is it

Answer 2

zeolite

heterogeneous catalyst

Question 3

products of cracking are mostly

Answer 3

alkenes

Question 4

understand octane rating

Answer 4

Hydrocarbons used in petrol (gasoline) are given an octane rating which relates to how effectively they perform in the engine. A hydrocarbon with a high octane rating burns more smoothly than one with a low octane rating.

Question 5

octane rating is higher

Answer 5

in the isomers with branched chains. e.g. octane number of heptane is 0; octane number in 2,2,4-trimethylpentane is 100

Question 6

isomerisation to increase octane rating condition

Answer 6

Pt catalyst on zeolite, 250 C, 13-30 atm

Question 7

understand aromatic hydrocarbons

Answer 7

ones based on a benzene ring

Question 8

how to improve the octane rating of hydrocarbons to be used in petrol

Answer 8

1. isomerisation, or 2. reforming

Question 9

conditions for reforming

Answer 9

a platinum catalyst suspended on aluminium oxide together with various promoters to make the catalyst more efficient. The original molecules are passed as vapours over the solid catalyst at a temperature of about 500°C.

Question 10

what happens in reforming

Answer 10

Isomerisation reactions occur (as above) but, in addition, chain molecules get converted into rings with the loss of hydrogen.

Question 11

reforming in hexane draw

Answer 11

hexane gets converted into benzene

http://www.chemguide.co.uk/physical/catalysis/petrochem.html

Question 12

reforming in heptane draw

Answer 12

heptane gets converted into methylbenzene

http://www.chemguide.co.uk/physical/catalysis/petrochem.html

Question 13

explain the use of crude oil as a source of both aliphatic and aromatic hydrocarbons

Answer 13

Crude oil is mainly a mixture of chains of carbon atoms. Some of these can be made into rings by a process called reforming, thus it is not only a source of aliphatic hydrocarbons but also of aromatic hydrocarbons

Question 14

kmno4 solution acidified with dilute h2so4

Answer 14

purple solution becomes colorless

Question 15

kmno4 solution made slightly alkaline (often by adding na2co3 solution)

Answer 15

the purple solution first becomes dark green solution, due to mno4 2- ions, and then produces a dark brown precipitate, due to solid mno2.

Question 16

chem eq oxidation of ethene with cold dilute kmno4 solution

name of product

Answer 16

CH2=CH2 + H2O + [O] -> HOCH2CH2OH

ethane-1,2-diol

Question 17

full ioinic eq oxidation of ethene with cold dilute acidified kmno4 solution

Answer 17

5CH2=CH2 + 2H2O + 2MnO4- + 6H+ -> 5HOCH2CH2OH + 2Mn2+

Question 18

full ioinic eq oxidation of ethene with cold dilute alkaline kmno4 solution

Answer 18

At first: CH2=CH2 + 2MnO4- + 2OH- -> HOCH2CH2OH + 2MnO42-

But eventually: 3CH2=CH2 +2MnO4- + 4H2O -> 3HOCH2CH2OH + 2MnO2 + 2OH-

Question 19

full ionic eq oxidation of ethene with cold dilute kmno4 solution

Answer 19

neutral

3CH2=CH2 +2MnO4- + 4H2O -> 3HOCH2CH2OH + 2MnO2 + 2OH-

Question 20

CH3CH=C(CH3)2 with hot concentrated acidified kmno4 solution produce.. (word and chemical eq)

Answer 20

CH3COOH + CH3COCH3

ethanoic acid + propanone

Question 21

C4H8: but-1-ene, but-2-ene, 2-methylpropene differences in products with hot concentrated acidified kmno4 solution

Answer 21

CH2=CHCH2CH3 + 5[O] -> CO2 + H2O + CH3CH2COOH
CH3CH=CHCH3 + 2[O] -> 2CH3COOH
CH2C(CH3)2 + 4[O] -> CO2 + H2O + CH3COCH3

Question 22

describe and explain the inductive effects of alkyl groups on the stability of cations formed during
electrophilic addition

Answer 22

Alkyl groups tend to push electrons away, thus carrying a partial positive charge, and the carbon they are attached to carrying a partial negative charge. The alkyl group has a positive inductive effect.

if a charge is very localized the ion is much less stable than if the charge is spread out over several atoms.

From primary(least stable) to secondary to tertiary(most stable) carbocation, more alkyl groups present places more and more negative charge on the positive carbon, reducing charge density and stabilizing it.

Question 23

recognise the difficulty of the disposal of poly(alkene)s, i.e. nonbiodegradability and harmful combustion products

Answer 23

the disposal of poly(alkene) plastic waste is difficult, as much of it is chemically inert and non-biodegradable. When burnt, waste plastics may produce toxic products, such as hydrogen chloride from PVC (poly(chloroethene)), dioxins, and toxic CO from incomplete combustion of the hydrocarbons.

Separating other plastic waste from the poly(alkene)s when objects have just been thrown away without being sorted according to their recycle code is another difficulty recycling plants have.

Question 24

Solutions to the difficulty of the disposal of poly(alkene)s

Answer 24

burn the poly(alkene)s and use the energy released to generate electricity, help conserve our supplies of fossil fuels that currently generate most of our electricity.

Acidic gases would have to be neutralised before releasing the waste gas into the atmosphere and very high temperatures used in incinerators to break down any toxins.

Question 25

describe and explain how the combustion reactions of alkanes make them suitable to be used as fuels in industry, in the home and in transport

Answer 25

Alkanes are useful as fuels because they are readily available, convenient to transport and use, burn cleanly into co2 and h2o (as long as there is an excess of air or oxygen), and have high enthalpy changes of combustion.

Question 26

recognise the environmental consequences of unburnt hydrocarbons arising from the internal combustion engine

Answer 26

Small amounts of unreacted hydrocarbons from the petrol-air mixture are found in the exhaust fumes. Hydrocarbons in the atmosphere can absorb infra-red radiation and play a part in the greenhouse effect.

Question 27

three major commercial uses of esters

Answer 27

solvents, perfumes, flavourings

Question 28

outline the use of infra-red spectroscopy in monitoring air pollution

Answer 28

it identifies compounds, in this case, air pollutants, based on the change in vibrations of particular atoms when infra-red radiation of specific frequencies is absorbed

Question 29

note: pokoknya kalo alkene + cold dilute kmno4, acidified or alkaline gk peduli apa, pkoknya organic productnya itu taro -OH to all yg involved in double bonds di alkene reactantnya

Answer 29

uwaaaaahhh nicenice gotchotiiiii

Question 30

hcooh + fehling’s solution

Answer 30

positive result. red ppt.

Question 31

hcooh + tollen’s reagent

Answer 31

positive result. silver mirror.

Question 32

ch3cooh + fehling’s solution

Answer 32

negative result. solution remains blue.

Question 33

ch3cooh + tollens’ reagent

Answer 33

negative result. no visible reaction.

Question 34

in the carboxylic acids homologous series, only hcooh will give (+) result with fehling and tollen due to the resemblance of its structure with aldehyde

Answer 34

ooowowowo

Question 35

What have halogenated hydrocarbons been used for?

Answer 35

solvents, refrigerants, monomers in polymer manufacture