Organic Chemistry Test (not containing Oxygen) 2.12.24 Flashcards

1
Q

name the formula: C2H4

A

ethene

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2
Q

what is a homologous series?

A
  • group of COMPOUNDS
  • with the SAME general formula
  • and the SAME functional group
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3
Q

give the stem on the name of a hydrocarbon that contains 1 carbon atom

A

meth-

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4
Q

give the stem on the name of a hydrocarbon that contains 2 carbon atoms

A

eth-

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5
Q

give the stem on the name of a hydrocarbon that contains 3 carbon atoms

A

prop-

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6
Q

give the stem on the name of a hydrocarbon that contains 4 carbon atoms

A

but-

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7
Q

give the stem on the name of a hydrocarbon that contains 5 carbon atoms

A

pent-

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8
Q

what is crude oil

A

a mixture of substances, mostly hydrocarbons

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9
Q

what are hydrocarbons

A

molecules containing only hydrogen and carbon

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10
Q

how do the boiling points of hydrocarbons change as the chain length gets longer (increases)

A

the longer the chain of hydrocarbons, the higher the boiling point

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11
Q

what is cracking?

A

the process of splitting long-chain hydrocarbons into (more useful) short-chain molecules

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12
Q

why do we need to crack hydrocarbons?

A

to meet the demand for smaller hydrocarbons, which are more useful

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12
Q

give the definition of a functional group

A
  • a group of atoms that determine how a compound typically reacts
  • members of a homologous series share the same functional group
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12
Q

what is the general formula of alkenes

A

CnH2n

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12
Q

what is the general formula of alkanes?

A

CnH2n+2

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13
Q

what is meant by general formula

A

an algebraic formula that can define any member of a family of compounds i.e. of a homologous series

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14
Q

what is meant by empirical formula

A

the simplest whole number ratio of each element in a compound

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15
Q

what is meant by molecular formula

A

the ACTUAL number of atoms of each element in a molecule

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16
Q

what is meant by displayed formula

A

shows how all the atoms are arranged and SHOWS ALL THE BONDS between them

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17
Q

what is meant by structural formula

A

shows the arrangement of atoms carbon by carbon, with the attached hydrogens and functional groups (read along, say what you see, e.g. ethene = CH2CH2)

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18
Q

why do members of a homologous series react in similar ways

A

they have the same functional group, i.e. the same ‘group of atoms that determine how a compound typically reacts’

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19
Q

name the compound CH2CHCH2CH3 (numbers here should be subscript)

A
  • 4x carbons in main chain so name starts with ‘but-‘
  • the main functional group is a carbon-carbon double bond, so it’s an alkene and will end with ‘-ene’
  • numbering the carbon chain such that one of the carbons in the C=C group hsd the lowest possible number means that the C=C group is on carbon 1 (the 1st carbon in the chain)
  • so the systematic name for the molecule is: but-1-ene
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20
Q

what is an isomer

A

iSoMerS are molecules with the SAME MOLECULAR formula but Different STRUCTURAL formulae

21
Q

give 3 types of isomerism

A
  1. differently shaped carbon chains
  2. functional groups in different places
  3. different functional groups
22
Q

describe the physical and chemical properties of isomers with differently shaped carbon chains (e.g. straight chain, branched)

A
  • similar chemical properties
  • different physical properties e.g. boiling point
    –> due to CHANGGE IN SHAPE of the MOLECULE
  • similar chemical properties
23
Q

do isomers with differently shaped carbon chains have similar or different chemical properties?

A

similar chemical properties

24
Q

do isomers with differently shaped carbon chains have similar or different physical properties? why/why not?

A
  • different physical properties
  • due to the change in shape of the molecule
25
Q

crude oil is a _ resource

A

finite

will run out eventually

26
Q

give 2 uses of crude oil??

A

fuels and feedstock for the petrochemical industry

27
Q

name and explain the process by which crude oil is separated into fractions

from rg notes

A

the process of fractional distillation:
1. the oil is heated until most of it has turned into gas
- gases enter fractionating column and the liquid part (bitumen) is drained off at the bottom
2. there is a temperature gradient in the fractionating column; it’s hotter at the bottom and cooler near the top.
- once the fractions (that make up crude oil) reach a part of the column where the temperature is lower than their b.p. they condense.
3. the longer hydrocarbons have high boiling points so they condense and drain out earlier on near the bottom of the column.
4. the shorter hydrocarbons have lower boiling points so they condense and drain out later near the top of the column whrtr it’s cooler.
5. bubble caps in the fractionating column prevent the separated liquids from running back down the column and remixing

28
Q

​ describe​ ​ how​ ​ the​ ​ industrial​ ​ process​ ​ of​ ​ fractional​ ​ distillation​ ​ separates
crude​ ​ oil​ ​ into​ ​ fractions

pmt notes

A
  • the oil is heated in the fractionating column and the oil evaporates and condenses at a number of different temperatures
  • the many hydrocarbons in crude oil can be separated into fractions, each of which contains molecules with a similar number of carbon atoms
  • the fractionating colomn works continuously, heated crude oil is piped in at the bottom. the vapourises oil rises up the column and the various fractions are constantly tapped off at the different levels where they condense
  • the fractions can be processed to produce fuels and feedstock for the petrochemical industry.
29
Q

list the fractions of crude oil, ordering them from lowest to highest boiling point

A

list the fractions of crude oil, ordering them from lowest to highest boiling point:
- refinery gases
- gasoline/petrol
- kerosine
- diesel
- fuel oil
- bitumen

raksha gets/preaches karma, dara finds batman.

30
Q

uses of refinery gases

A

domestic heating and cooking

31
Q

uses of gasoline/petrol

A

fuel for cars

32
Q

uses of kerosine

A

fuel for aircraft / “aviation fuel”

33
Q

uses of diesel

A

fuel in larger vehicles e.g. trains

34
Q

uses of fuel oil

A
  • fuel for large ships
  • fuel in some power stations
35
Q

uses of bitumen

A

to surface roads and roofs

36
Q

give 3 physical properties of shorter hydrocarbons

A
  • shorter molecules have a lower boiling point, so they will also vaporise/condense at lower temperatures
  • they are much thinner i.e. less viscous
  • they are paler in colour
37
Q

give 3 physical properties of longer hydrocarbons

A
  • much higher boiling points, so they vaporise/condense at higher temperatures
  • more viscous (thick & gloopy)
  • darker in colour
38
Q

which are in higher demand, shorter or longer hydrocarbons?

A

there is a much higher demand for shorter hydrocarbons

39
Q

which is there a greater supply of, shorter or longer hydrocarbons?

A

there is a greater supply of longer hydrocarbons
so
we use cracking to break them down into shorter molecules

40
Q

what is a fuel?

A

a substance that releases energy when burned

41
Q

why are hydrocarbons good fuels?

A

they realease lots of energy when burnt
i.e. the reactions are very exothermic…

42
Q

​ describe​ ​ how​ ​ long-chain​ ​ alkanes​ ​ are​ ​ converted​ ​ to​ ​ alkenes​ ​ and
shorter-chain​ ​ alkanes

A

by​ ​ catalytic​ ​ cracking:
- in industry, vaporised hydrocarbons are passed over a powdered catalyst - either silica (SiO2) or alumina (Al2O3) - at about 600-700 degrees Celcius.

cracking requires heat & a catalyst

43
Q

what type of reaction/process is cracking?

A

cracking is a form of thermal decomposition

44
Q

what types of molecules are produced from cracking

A

cracking:
long-chain ahydrocarbon molecule –> shorter alkane molecule + alkene

45
Q

define the term saturated

A

compounds with only SINGLE BONDS between the carbon atoms

46
Q

define the term unsaturated

A

compounds with one or more carbon-carbon double bond (C=C)

47
Q

are alkanes saturated or unstaturated

A

saturated

48
Q

are alkenes saturated or unstaturated

A

unsaturated (contain C=C bond)

49
Q

​ explain​ ​ why​ ​ cracking​ ​ is​ ​ necessary,​ ​ in​ ​ terms​ ​ of​ ​ the​ ​ balance​ ​ between
supply​ ​ and​ ​ demand​ ​ for​ ​ different​ ​ fractions

from pmt notes

A
  • much greater demand for smaller chained alkanes than longer chained alkanes
  • however, there is a greater supply for longer chained alkanes
  • therefore an alternative to produce smaller chained alkanes is required (i.e. cracking)
50
Q

what conditions do alkanes need to react with halogens?
what are the products
what happens to hydrogen?

A
  • only if in presence of UV light
  • produces haloalkanes
  • in these reactions - SUBSTITUTION REACTIONS - a hydrogen atom from the alkane is substituted with (replaced by) a chlorine or a bromine
  • this is how bromine and methane react together to form bromomethane:
    -methane + bromine –> bromomethane + hydrogen bromide
51
Q

under certain conditions, halogens react with alkanes to make haloalkanes.
1. name the required condition(s).
2. state what type of reaction this is

A
  1. presence of UV light
  2. substitution reaction (bc a hydrogen atom in the alkane is replaced by a halogen - usually chlorine or bromine)
52
Q

how does the presence of double carbon-carbon bonds in alkenes affect reactivity?

A

having a C=C double bond makes alkenes HIGHLY REACTIVE

53
Q

do halogens react with alkenes?
what products are formed?
what happens to the alkene?

A
  • YES - halogens and alkenes react to form haloalkanes
  • the C=C double bond is SPLIT and a halogen atom is added to each of the carbons
  • therefore these are ADDITION reactions
  • for example:
    ethene + bromine –> dibromoethane
54
Q

how do you test for C=C double bonds?

A

use the reaction between bromine and alkenes: