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Chemistry > 4.1 > Flashcards

4.1 Flashcards

1
Q

a) what are the names corresponding to the first ten members of the alkanes homologous series and the corresponding alkyl groups?

A

1 : methane : methyl
2 : ethane : ethyl
3 : propane : propyl
4 : butane : butyl
5 : pentane : pentyl
6 : hexane : hexyl
7 : heptane : heptyl
8 : octane : octyl
9 : nonane : nonyl
10 : decane : decyl

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2
Q

Name for alkanes?

A

-ane

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3
Q

Functional group and name for alkenes?

A

C=C : -ene

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4
Q

Functional group and name for haloalkane?

A

C-X (where X is a halogen) : halo- (e.g. bromo-)

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5
Q

Functional group and name for alcohols?

A

C-OH : hydroxy- or -ol

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6
Q

Functional group and name for aldehydes?

A

R-C=O (where R is other organic stuff) : oxo- or -al
|
H

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7
Q

Functional group and name for ketone?

A

R-C=O (where R is organic stuff but not hydrogen) : oxo- or -one
|
R

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8
Q

Functional group and name for carboxylic acid?

A

-C=O : -oic acid
|
OH

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9
Q

Functional group and name for esters?

A

-C=O : alkyl -anoate
|
O-
With the alcohol contributing the alkyl, and the acid contributing the -anoate

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10
Q

b) i) What is the general formula?

A

The simplest algebraic formula of a member of a homologous series.

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11
Q

b) ii) What is the structural formula?

A

The minimal detail that shows the arrangements of atoms in a molecule (CH3CH2CH3)
Ester: COO
carboxylic acids: COOH

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12
Q

b) iii) What is the displayed formula?

A

The relative positioning of atoms and the bonds between them.

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13
Q

b) iv) What is the skeletal formula?

A

A displayed formula with the hydrogens having been removed from the alkyl chains.

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14
Q

c) i) What is the definition of a homologous series?

A

A series of organic compounds which have the same functional group but with each successive member differing by CH2.

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15
Q

c) ii) What is a functional group?

A

A group of atoms responsible for the characteristic reactions of a compound.

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16
Q

c) iii) What is an alkyl group?

A

A compound of formula CnH2n+1

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17
Q

c) iv) what is an aliphatic?

A

A compound containing carbon and hydrogen joined together in straight or branched chains, or non-aromatic rings.

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18
Q

c) v) What is an alicyclic

A

An aliphatic compound arranged in non-aromatic rings with or without side chains.

19
Q

c) vi) What is an aromatic?

A

A compound containing a benzene ring.

20
Q

c) vii) What is a saturated compound?

A

A compound which contains only single carbon-carbon bonds.

21
Q

e) What are structural isomers?

A

Compounds with the same molecular formula but different structural formulae.

22
Q

f) What are the different types of covalent bond fission?

A

Homolytic fission: where each bonding atom receives one electron from the bonded pair, forming two radicals.
Heterolytic fission: where one of the bonding atoms receives both electrons from the bonded pair.

23
Q

g) What is the definition of a radical?

A

A species with an unpaired electron. It is shown by a dot.

24
Q

h) What does a curly arrow represent?

A

The movement of an electron pair.

25
Q

a) What are alkanes?

A

Saturated hydrocarbons containing sigma bonds

26
Q

a) What are sigma bonds?

A

Molecular orbitals where the overlap of the orbitals are directly between the bonding atoms.

27
Q

b) What shape are alkanes?

A

The shape, determined by electron pair repulsion theory, is tetrahedral around each carbon atom with bond angles of 109.5° throughout as each carbon has four bond pairs and no lone pairs.

28
Q

c) How does boiling point change with different length and branching alkanes?

A

In straight chain alkanes, the boiling point increases with the length. This is because the number of electrons in the molecule increases, which increases the London forces, so more energy is then required to overcome the intermolecular forces.
In isomeric alkanes, the boiling point decreases as the isomers become more branched. This is because they have a smaller surface area for the London forces to act through, so there is a smaller attraction between molecules.

29
Q

d) Why aren’t alkanes very reactive?

A

Alkanes are the most basic homologous series as they have no functional group.
This means that they have no centre where reactions tend to happen because C-C and C-H bonds are both strong and non-polar due to their very slight differences in electronegativity. This means they attract no other charged compounds or atoms.
All the covalent bonds in alkanes also have high bond enthalpy so energy is not easily released during reactions.

30
Q

Reaction mechanism for alkanes and halogens:

A

The reaction mechanism is free radical substitution: where a radical replaces a different atom or group of atoms. (CH4 + Cl -UV-> CH3Cl + HCl
1. Initialisation: where radicals are generated by UV light, homolytic fission (or 300°C): Cl2 -UV-> 2Cl•
2. Propagation: the two repeated steps in radical substitution that build up the products in a chain reaction: Cl• + CH4 -> HCl + CH3• / CH3• + Cl2 -> CH3Cl + Cl•
3. Termination: the step at the end of radical substitution when two radicals combine to form a molecule: Cl• + CH3• -> CH3Cl / 2Cl• -> Cl2 / 2CH3• -> C2H6

The possibility of multiple substitution of initially formed products exist. (Most likely: CH3Cl -> CH2Cl2 -> CHCl3 -> CCl4 :least likely). All these side products can be separated by fractional distillation or chromatography.

31
Q

What are π-bonds?

A

Molecular orbitals which have a sideways overlap of adjacent p-orbitals above and below the bonding carbon atoms. They have restricted rotations.

32
Q

Reaction mechanism for hydrogenation of alkenes:

A

Hydrogenation is an addition reaction in which hydrogen is added across a double bond.
Conditions: Nickel and 150°C.
Example equation: C2H4 + H2 -> C2H6

33
Q

Reaction mechanism for hydrohalogenation of alkenes:

A

Procedure: Bubble XH through alkene at room temperature.
Mechanism: C=C bond -curly arrow-> Hδ+, H-X bond -curly arrow-> X (forming a carboncation) —> :Br- -curly arrow-> C+

34
Q

Reaction conditions for hydration of alkenes

A

Steam (65atm, 300°C), and H3PO4

35
Q

What is stereoisomerism?

A

When organic compounds have the same molecular formula and structural formula, but different arrangements of atoms in space.

36
Q

How do you determine E/Z isomerism?

A

Use CIP rules to determine the priority of the atoms bonded to the C=C based on their relative atomic mass.
If the highest priority atoms are on the same side, the isomer is Z. If the highest priority atoms are on different sides, the isomer is E.

37
Q

How do you determine cis-trans isomerism?

A

Cis-trans isomerism is a special type of E/Z isomerism where two substituents on each carbon atom are the same. E is trans. Z is cis.

38
Q

What are alkenes?

A

A homologous series of unsaturated hydrocarbons which have the general formula CnH2n

39
Q

What is the bonding in alkenes like?

A

A σ-bond is formed between two carbon atoms using the direct overlap of electron clouds of the two atoms. The π-bond is formed by the electrons in adjacent p-orbitals overlapping above and below the carbon atoms. The π-bond has restricted rotation, so alkene molecules are planar in the region of the double bond.

40
Q

What is the shape of alkene molecules?

A

Each carbon atom in the molecule has three areas of electron density. There will be two covalent bonds to separate hydrogen atoms, and one σ-bond and one π-bond between the two carbon atoms. Each of these electron densities repel by the same amount forming bond angles of 120°, which results in a trigonal planar shape.

41
Q

Why are alkenes more reactive?

A

π-bonds have lower bond enthalpies than σ-bonds so will break more easily and react, leaving the σ-bond between the two carbon atoms.
In addition to this, the double bond is an area of high electron density so is more prone to electrophile attacks.

42
Q

Reaction mechanism for halogenation of alkenes:

A

Reaction mechanism: electrophilic addition.
Conditions: halogen.
Mechanism: C=C bond -curly arrow-> Brδ+ (induced dipole), Brδ+-Brδ- bond -curly arrow-> Brδ- —> :Br- -curly arrow-> C+

43
Q

What is Markownikoff’s rule?

A

Markownikoff’s rule states that primary carbocations (bonded to one carbon chain) are less stable than tertiary carbocations (bonded to three carbon chains).
Therefore when H-X reacts with an alkene the hydrogen will become attached to the carbon with the most hydrogen atoms to start with.

44
Q

How do we manage polymer waste?

A

-combustion for energy production. Could cause HCl if a halogenated plastic.
-use as an organic feedstock for the production of other organic chemicals.
-reusing.

The development of biodegradable and photodegradable polymers which breaks down the polymer chains into small pieces. This would reduce dependency on finite resources and alleviate the problems from disposal.

Chemistry (17 decks)

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