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Chemistry (N.A.) > UNIT 11 Organic Chemistry > Flashcards

UNIT 11 Organic Chemistry Flashcards

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1
Q

syllabus

  • Draw and interpret the displayed formula of a molecule to show all the atoms and all the bonds
  • Name and draw the displayed formulae of:
    (a) methane and ethane
    (b) ethene
    (c) ethanol
    (d) ethanoic acid
    (e) the products of the reactions stated in
    sections 11.4–11.7 - WHICH IS:
  • Name and draw the structural and displayed
    formulae of unbranched:
    (a) alkanes
    (b) alkenes, including
    but-1-ene and but-2-ene
    (c) alcohols, including
    propan-1-ol, propan-2-ol, butan-1-ol and
    butan-2-ol
    (d) carboxylic acids
    containing up to four carbon atoms per molecule
  • Name and draw the displayed formulae of the unbranched esters which can be made from unbranched alcohols and carboxylic acids, each containing up to four carbon atoms
  • State the type of compound present, given a chemical name ending in -ane, -ene, -ol, or -oic acid or from a molecular formula or
    displayed formula
A
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2
Q

hydrocarbons

as chain length increases…

A

molecules that consist of only carbon and hydrogen atoms

boiling point INCreases.

∴ small chains = often gases, longer chains = liquids, extremely long chains = solids

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3
Q

a structural formula is…

A

an
unambiguous description of the way the atoms
in a molecule are arranged, including CH2=CH2, CH3CH2OH, CH3COOCH3

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4
Q

Define structural isomers

A

compounds with the
same molecular formula, but different structural
formulae,

including C4H10 as CH3CH2CH2CH3 and
CH3CH(CH3)CH3

and C4H8 as CH3CH2CH=CH2 and CH3CH=CHCH3

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5
Q

Write and interpret general formulae of
compounds in the same homologous series,
limited to:

alkanes
alkenes
alcohols
carboxylic acids

A

a) alkanes, CnH2n+2

(b) alkenes, CnH2n

(c) alcohols, Cn H2n+1 OH

(d) carboxylic acids, Cn H2n+1 COOH

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6
Q

hydrocarbons

A

compounds that
contain hydrogen and carbon only

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7
Q

petroleum (crude oil) is …

A
  • a MIXTURE of HYDROCARBONS
  • can be separated into useful fractions by FRACTIONAL DISTILLATION
  • as the different hydrocarbons have different chain lengths and ∴ different boiling points
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8
Q

DESCRIBE: separation of petroleum into useful fractions by fractional distillation

A

crude oil is heated until molecules evaporate, go into heat gradient tower. Once it has produced vapor, this cools and is separated into different fractions based on their boiling point

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9
Q
A
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10
Q

functional group

A

an atom or group of atoms that determine the chemical properties of a homologous series

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11
Q

a homologous series is…

A

a family of similar compounds with similar chemical properties due to the presence of the same functional group

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12
Q

Describe the general characteristics of a
homologous series

A

(a) having the same functional group

(b) having the same general formula

(c) differing from one member to the next by
a –CH2– unit

(d) displaying a trend in physical properties

(e) sharing similar chemical properties

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13
Q

a saturated compound has…

A

molecules in which all carbon–carbon bonds are single bonds

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14
Q

an unsaturated compound has …

A

molecules in which one or more carbon–carbon bonds are not single bonds

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15
Q

Name the fossil fuels

A

coal, natural gas and
petroleum

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16
Q

Name methane as…

A

the main constituent of
natural gas

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17
Q

important rule about CARBON and valence electrons

A

carbon has 4 valence electrons

carbon always forms FOUR bonds

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18
Q

different formula - molecular, structural, empirical

A

molecular: reps the number & type of diff atoms in one molecule

structural: desc of the way the atoms in a molecule are arranged

empirical: simplest whole number ratio of the different atoms in a compound

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19
Q

functional groups of alkanes, alkenes, alcohol, carboxylic acid, ester

naming

general formula

e.g.s - DRAW them

A

alkAnes: ONLY single C-C bond
-ane
CnH2n+2

alkEnes: C=C bond
-ene
Cn H2n

alcohol: at least one –O-H group
-ol
Cn H2n+1 OH

carboxylic acid: a C=O AND an –O-H group
-oic acid
Cn H2n O2

ester: a C=O AND an –O-R group
-yl
-oate

haloalkanes
single bonds only AND at least one halogen (Cl, Br, F, I)
Cn H2n+1 X

alkynes
triple C to C bond
Cn H2n-2

amines
C-NH2
Cn H2n+1 NH2

20
Q

naming organic compounds

  1. prefix = number of CARBONS in the longest chain
  2. suffix = FUNCTIONAL group
  3. TYPE of bonding in the carbon chain - ‘an’ (single bond) or ‘en’
  4. where the functional group is placed on the chain (LOWEST number possible - so e.g. going from left = 2, from right = 4. 2 lower) SO - this is the number that goes after ‘an’/’en’
A

pent

an

2

ol

pentan-2-ol

21
Q

3 carbon chain gives prefix

1 meth-
2 eth-
3 prop-
4 but-

monkeys eat peanut butter

pent, hex, hept, oct

A

prop

22
Q

desc bonding & properties of alkanes

A
  • C-C and C-H bonds = COVALENT single bonds
  • C and H atoms SHARE electrons to form full valence shells
23
Q

what do we call this bonding

KEY WORD.

A
  • bonding SATURATED as the carbon is bonded to the maximum number of atoms (FOUR)
24
Q

chemical properties

A

other than COMBUSTION,

generally unreactive

25
Q

combustion w/ alkanes in EXCESS O2

e.g., methane, COMPLETE

CH4 (g) + 2O2 (g) -> CO2 (g) + 2H2O (l)

A
  • in excess oxygen, alkanes burn w/ a blue flame
  • in COMPLETE combustion, form CO2 and H2O
26
Q

combustion alkanes LIMITED O2

e.g., ethane, incomplete

2C2H6 (g) + 5O2 (g) -> 4CO (g) + 6H2O (l)

A
  • in limited O2, alkanes burn w/ yellow/sooty flame
  • in INcomplete combustion, form CO (+carbon/soot) AND H2O
27
Q

physical properties

  • COLOUR: all colourless
A

small chain alkanes: gases at room temp (lower BP)

  • due to very weak intermolecular forces.

WHILE larger chain alkanes are liquids at room temp (higher BP)

  • due to stronger intermolecular forces

+ densities between 0.6 and 0.8 g/cm3, so they are less dense than water.

28
Q

substitution reaction of alkanes with chlorine / sub w/ halogens

e.g., ethane, cl2

C2H6 + Cl2 -> C2H5Cl +HCl
chloroethane

A
  • when an atom attached to a C is replaced by another atom
  • form haloalkane
  • a -H atom is replaced by a halogen atom (-Cl) to form 2 new bonds: H-Cl, C-Cl.
  • due to unreactive nature of alkanes, this is: a SLOW reaction + needs a UV LIGHT CATALYST.
29
Q

properties of alkenes

same as alkanes

A
  • colourless
  • insoluble in water, forms 2 layers
  • less dense than water
  • small chain alkenes => gases
  • longer chain length => liquids at room temp [stronger intermolecular forces]
30
Q

addition reactions with bromine, hydrogen & steam

A

[CARD]

31
Q

distinguish btwn saturated & unsaturated hydrocarbons by reaction with aqueous bromine

  • test for saturation with Br2 [RED-BROWN]
A

C2H4 + Br2 => C2H4Br2

alkene goes colourless, forms a dihaloalkane

while, alkane + Br2 => remains red-brown

32
Q

unsaturated bonding

A

the carbon is NOT bonded to the maximum number of atoms (4); [double/triple] bonds can be broken & atoms added

  • alkEnes & alkynes UNSATURATED
    while alkanes & alcohols are saturated.
33
Q

desc manufacture of alkenes and
hydrogen by the cracking of larger alkane
molecules using a high temperature and a
catalyst

A
  • heating the hydrocarbon molecules to around 600 – 700°C to vaporise them
  • vapours then pass over a hot powdered catalyst of alumina or silica
  • process breaks covalent bonds in the molecules as they come into contact with the surface of the catalyst, causing thermal decomposition reactions
  • molecules are broken up in a random way which produces a mixture of smaller alkanes and alkenes
  • Hydrogen and a higher proportion of alkenes are formed at higher temperatures and higher pressure
34
Q

what is cracking

A

-

35
Q
A
36
Q
A
37
Q

alkenes => alcohols

A
  • addition with H2O (g) with acid catalyst
  • the C=C double bond breaks and one hydrogen atom and one OH group is added to the carbons of the double bond
  • the alkene has one -H atom and one -OH (hydroxyl group) added to form an alcohol
38
Q

alcohols used as…

A
  • fuels (flammable) for vehicles
  • solvents (many substances soluble in short chain alcohols) - for paint varnishes
39
Q

alcohol combustion - ethanol, complete combustion and burn in excess oxygen to produce carbon dioxide and water

A

C2H5OH (l) + 3O2 (g) → 2CO2 (g) + 3H20 (l)

40
Q

4 main types of alcohol reactions

A

oxidation, dehydration, substitution, esterification

41
Q

oxidation

A
  • Primary alcohols can be oxidised to formaldehydeswhich can undergo further oxidation to formcarboxylicacids
  • Secondary alcohols can be oxidised to formketonesonly
  • Tertiary alcohols do not undergo oxidation
  • The oxidising agents of alcohols includeacidified K2Cr2O7oracidified KMnO4
42
Q

dehydration

undergo this to form?

what happens?

A

-alcohols undergodehydrationto form alkenes

  • Alcohol vapour is passed over ahot catalystof aluminium oxide (Al2O3) powder OR pieces of porous pot or pumice as well as concentrated acid can be used as catalysts
43
Q

define dehydration reaction

A
  • a type ofeliminationreaction
  • a reaction in which a water molecule is removed from a larger molecule
44
Q

e.g.

A

Ethanol (C₂H₅OH) → Ethylene (C₂H₄) + Water (H₂O)

45
Q

substitution of alcohols

  • ## replaced by?
A
  • In thesubstitutionof alcohols, a hydroxy group (-OH) is replaced by a halogen to form anhalogenoalkane
  • can be achieved by reacting the alcohol with:

📍 HX (rather than using HBr, KBr is reacted with H2SO4or H3PO4to make HBr that will then react with the alcohol)
📍 PCl3and heat
📍 PCl5at room temperature
📍 SOCl2

46
Q

esterification

A

-condensationreaction between a carboxylic acid and an alcohol to form anester and a water molecule

  • carboxylic acid and alcohol areheated under refluxwith astrong acid catalyst(such as H2SO4or H3PO4)
  • Carboxylic acid + alcohol → ester + water
  • The reaction is reversible so an equilibrium mixture can be established with all the reactants and products

-Esters havesweet,fruity smells

Chemistry (N.A.) (10 decks)

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