Module 4.1 - Basic Concepts and Hydrocarbons Flashcards

Question

What is an alkyl group with one carbon chain called?

Answer 1

The smallest whole number ratio of atoms of the elements in a compound

Answer 2

1. Calculate the number of moles of each element (n=m/Mr) 2. Divide by the smallest value 4. Change the ratio to whole numbers 5. Write the formula

Answer 3

The numbers and types of atoms in a compound

Answer 4

1. Calculate the relative empirical mass using the empirical formula 2. Divide the relative molecular mass by the empirical formula 3. Multiply each atom in the empirical formula by the number calculated in step 2 and write the molecular formula

Answer 5

Useful when considering the shape/size of a molecule but this is time consuming + easy to draw complex molecules incorrectly

Answer 6

- give a feel for the arrangement of atoms in a molecule + can be drawn quickly - physical properties often relate to chain length + branching, making this type of representation useful

Answer 7

- the chemistry of organic compounds is often related to their functional groups - skeletal formula focuses the attention on this part of the molecule - often used in constructing mechanisms e.g. flow charts that model electron movement in chemical reactions

Answer 8

Simplified structural formula drawn by removing hydrogen atoms from alkyl chains

Answer 9

Organic chemicals containing at least one carbon-carbon double covalent bond

Answer 10

Compounds that contain only hydrogen and carbon

Answer 11

An organic compound containing only single covalent bonds

Answer 12

Skeletal formula

Answer 13

- the electrons are shared across all the carbon atoms | - this part of the molecule is rarely involved in the chemical reactions + is often represented using skeletal formula

Answer 14

Brake fluid

Answer 15

Cyclohexane

Answer 16

- alkyl groups in different places - functional groups bonded to different parts of parent chain (e.g. primary alcohol, secondary alcohol, tertiary alcohol) - different functional groups e.g. aldehyde vs ketones

Answer 17

Compounds with the same molecular formula but a different structural formula

Answer 18

A group of atoms responsible for the chemical reactions of a compound

Answer 19

Organic compounds with the same molecular formula and structural formula but have a different arrangement of atoms in space

Answer 20

A type of E/Z isomerism in which the two substituent groups attached to both carbon atoms of the C=C double bond are the same

Answer 21

A type of stereoisomerism caused by the restricted rotation around the double bond - the two different groups attached to both carbon atoms of the C=C double bond

Answer 22

1. Locate the C=C double bond in the molecule + redraw it to show the substituents 2. Focus on one carbon atom and assign the priority of each substituent based on its relative atomic mass - the highest is given the highest priority. Then assign the priority of the second carbon atom 3. If the highest priority groups are on the same side of the C=C double bond, then the isomer is Z. If the highest priority groups are on different sides of the C=C double bond, then the isomer is E

Answer 23

Electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

Answer 24

Two highly reactive, neutral species called radicals

Answer 25

When a covalent bond breaks + each electron from the covalent bond goes to different bonded atoms

Answer 26

X-Y --> X. + Y.

Answer 27

Cl-Cl --> 2Cl. - UV radiation causes the covalent bond to break - one electron from the covalent bond goes to each chlorine atom

Answer 28

When a covalent bond breaks and both electrons go to one of the bonded atoms, resulting in a positive and a negative ion X-Y --> X+ + Y- E.g. The dipoles on the carbon and bromine on 2-bromopropane can cause heterolytic fission under certain circumstances and therefore leave a carbocation and a bromide ion

Answer 29

A covalent bond forms

Answer 30

Because they're unstable

Answer 31

Tetrahedral, 109.5º

Answer 32

Overlap of the electron clouds from each atom making a sigma bond

Answer 33

Electronegativity of hydrogen and carbon is very similar so no significant dipoles form

Answer 34

- electrons moving around the shells occasionally causes lack of balance of charge distribution - causes an instantaneous dipole - induces dipoles on neighbouring molecules - causes induced dipole-dipole interactions: London forces

Answer 35

- precise temp that substance changes from gas to liquid or vice versa - as bp changes with pressure, standard vales are given in K at 100kPa

Answer 36

- as alkane chains get longer their relative molecular mass increases - larger molecules have more areas of surface contact between adjacent molecules - increases the number of induced dipole-dipole forces (more London forces) - more energy needed to overcome the intermolecular attraction so it can change state - positive correlation when chain length plotted against bp

Answer 37

- more branching = fewer areas of surface contact as molecules can't pack together as closely - branched molecules have fewer London forces than the straight chain isomer with the same molecular formula - branched molecules have a lower bp than the equivalent straight chain isomer

Answer 38

- all the covalent bonds in alkane molecules have high bond enthalpies (large amounts of energy required to break the bonds) - the carbon-hydrogen sigma bonds have very low polarity because carbon + hydrogen's electronegativities are almost the same

Answer 39

- fuels | - undergo combustion transferring stored chemical energy to a usable form e.g. thermal energy

Answer 40

Rapid oxidation reaction combining oxygen (usually from air) with another substance

Answer 41

Plentiful supply of air (oxygen)

Answer 42

Clean, blue flame transferring max amount of thermal energy as fully oxidises carbon and hydrogen

Answer 43

CH4 + 2O2 --> CO2 + 2H2O

Answer 44

When there is a limited supply of air (oxygen)

Answer 45

2CH4 + 2 1/2O2 --> CO + C + 4H2O 2CH4 + 3 1/2O2 --> CO2 + CO + 4H2O 3CH4 + 4 1/2O2 --> CO2 + CO + C + 6H2O

Answer 46

- homolytic fission of halogen molecules forming radicals - hydrogen atom is substituted for a halogen atom - if reaction conditions maintained, substitution can continue until all H atoms replaced in original alkane by halogen atoms

Answer 47

- initiation: homolytic fission causing the formation of 2 radicals - propagation: two repeated steps that build up the desired product in a side reaction - termination: two radicals collide to make a stable product

Answer 48

Reactions are randomly caused by a v reactive radical colliding with another species

Answer 49

- mixture of products is formed | - chromatography or fractional distillation needed to separate products before they can be used

Answer 50

Cl2 --> 2Cl• | -UV light or temps of about 300ºC needed

Answer 51

CH4 + Cl• --> •CH3 + HCl •CH3 + Cl2 --> CH3Cl + Cl• -step 1 generates an alkyl radical and a hydrogen chloride -step 2 generates the desired product + regenerates the chlorine radical

Answer 52

2Cl• --> Cl2 2•CH3 --> C2H6 •CH3 + •Cl --> CH3Cl Mixture of products formed by the random collisions between radicals. Low atom economy as only one desired product (CH3Cl)

Answer 53

Chloromethane molecules molecules may collide agin with other chloride radicals causing further substitutions

Answer 54

``` Initiation: Br2 --> 2Br• Propagation: C2H6 + Br• --> •C2H5 + HBr •C2H5 + Br2 --> C2H5Br + Br• Termination: 2Br• --> Br2 2•C2H5 --> C4H10 •C2H5 + Br• --> C2H5Br ```

Answer 55

- sigma bond formed between 2 carbon atoms using the direct overlap of electron clouds of two atoms (s or p orbitals) - pi bonds formed by electrons in adjacent p-orbitals overlapping above and below the carbon atoms. Can only be made after a sigma bond has been formed

Answer 56

Holds atoms in position by restricting rotation around the double bond, hence alkenes have a flat shape in the region of the double bonds

Answer 57

Trigonal planar. 120º

Answer 58

Pi bond because of the high electron density around it

Answer 59

- 2 separate covalent bonds between C atoms + two different H atoms (sigma bond) - covalent bond between the 2 C atoms, made from a sigma and a pi bond

Answer 60

The restricted rotation around the double bond

Answer 61

- alkenes due to the double bond - bond enthalpy for C-C is +347kJmol^-1 and for a C=C bond is +612kJmol^-1, meaning bond enthalpy of pi bonds is (612-347=265kJmol^-1) - in chemical reactions the pi bonds break first as lower bond enthalpy and react leaving the sigma bond between the two carbon atoms - double bond is an area of high electron density attracting electrophiles e.g. Br2, HBr + NO2+

Answer 62

Two or more molecules become bonded to make one product

Answer 63

An addition in which hydrogen is added across the C=C bond of an alkene

Answer 64

150ºC, nickel catalyst, hydrogen (alkene)

Answer 65

An addition reaction in which a halogen is added across the C=C double bond becoming a saturated dihaloalkane (can be used to test for saturation)

Answer 66

Bromine/iodine solution mixed w a saturated compound there's no reaction. When added to an unsaturated compound e.g. ethene, decolorisation occurs as an addition reaction occurs

Answer 67

- bromine is non polar - when the bromine molecule becomes close to the electron rich C=C bond a dipole is induced on the bromine molecule - ∂+ side of the molecule is attracted to the electron density of the C=C bond - electrons from π bond make bond w a bromine atom - causes heterolytic fission of the bromine molecule - +ve charge remains on second carbon atom - leaves a v reactive species known as a carbocation - 2 electrons from the bromide ion are shared with the carbocation, making a second bond and a stable product

Answer 68

An electron pair acceptor

Answer 69

To make alcohols

Answer 70

A model showing the movement of electrons in an organic reaction

Answer 71

- phosphoric acid catalyst - 300ºC - 65 atm - H2O reagent

Answer 72

A haloalkane

Answer 73

- large difference in electronegativity between H and Br so a HBr molecule is polar. H (delta +) of HBr is attracted to the high electron density of C=C bond - electrons in pi bond make a bond w the H causing heterolytic fission (electrons in HBr molecule given to Br atom making a Br- atom). Carbocation also made - Br- ion + carbocation bond to make a stable product

Answer 74

When H-X is added to an unsymmetrical alkene the H become attached to the C with the most H atoms to start with

Answer 75

Carbocations that have alkyl groups attached are more stable than those with H atoms attached

Answer 76

- poly(ethene) | - plastic bags + bottles

Answer 77

- poly(propene) | - ropes + crates

Answer 78

- poly(chloroethene) (PVC) | - electrical cable insulation

Answer 79

- poly(phenylethene) (polystyrene) | - packaging

Answer 80

- poly(tetrafluoroethene) (Teflon) | - non-stick coatings on cooking pans

Answer 81

1. Draw the monomer structure so the C=C bond is the focus of the diagram 2. Draw square brackets around the monomer 3. Change the C=C to C-C + draw 2 lines extending from each C atom through the square brackets 4. Add a subscript 'n'

Answer 82

- clothing | - materials in cars

Answer 83

due to their versatility

Answer 84

- saturated organic compounds + so are very stable - don't get attacked by environmental conditions/microorganisms so remain chemically unchanged for hundreds of years - made from compound made available from processing crude oil (non renewable resource, being used faster than planet's natural processes can make it so may come a time where we can't use it)

Answer 85

- landfill - combustion - combustion with electrical generation - reusing - recycling - using them as organic feedstock

Answer 86

- large holes dug into landscape, lined to stop contaminants seeping into water table. Rubbish put into holes + compacted. When site full its copped + landscape - after buried conditions change from normal atmospheric to anaerobic + often limited supply of water. Reduces rate of biodegradable material's decomposition. As many plastics are non biodegradable the waste doesn't break down + can become a danger to wildlife

Answer 87

- plastics: mainly organic + can be burnt. Contain large amounts of carbon so combustion releases CO2 (greenhouse gas linked to climate change) - depending on plastic other toxin/polluting gases (e.g. HCl) can be made. Can be removed by using gas scrubbers, where a base (e.g. CaO) neutralises acidic gas - plastics: high calorific value so can be burnt in power stations. Chemical energy transferred can be used to drive turbines + generate electricity

Answer 88

- plastics have to be sorted into different types, expensive as either labour intensive or uses costly high technology to automate the process - plastics cleaned, melted down + reshaped to new products. Limited market for recycled plastic companies concerned about quality + whether or not there could be contamination from its previous use

Answer 89

when plastics sorted into different types, a series of chemical reactions can be used to break down the plastic polymers into small organic molecules, allowing recovered chemicals to be used in other industrial reactions

Answer 90

- e.g. plant starch - research into plastics that can be broken down chemically by microorganisms + environmental factors into harmless (even useful) substances. Sometimes mixed w an addition polymer. Starch part breaks down so polymer chain smaller + the material biodegrades. Growing concern small pieces of addition polymers still cause hazards to ecosystem - if only bio polymer used new material called bioplastic. Plant starch used to make bin bags. If starch derived from sustainable farming methods then material classified 'carbon neutral' - to be fully decomposable plastic must decompose landfill about as quickly as compost forms from grass clipping + other green waste. Only products should be CO2, H2O, inorganic compounds + biomass - substances e.g. poly(lactic acid) decompose in about 180 days + currently being used to make cold-drink cups + wrap fresh fruit + vegetables

Answer 91

- break down chemically using energy w wavelengths similar to light. either adition polymers w bonds within their structures weakened by absorption of light or have an additive affected by light, which weakens bonds within the polymer. Once polymer exposed to light, begins to break down + not possible to stop process - photodegradable plastics in landfill may not be exposed to sufficient light to degrade

Module 4.1 - Basic Concepts and Hydrocarbons Flashcards

(139 cards)