Explain CH4 tetrahedral shape? (2-way)

- 4 Sp3 hybrid orbitals repel each other equally - Guess they 109.5° apart

Write/"draw" a propagation stage example? (CH4 w/ Cl)

CH4 + Cl˙ -> ˙CH3 + HCl then ˙CH3 + Cl2 -> CH3Cl + ˙Cl , there's even a mechanism drawing here but meh.

C Unit 2.5 Hydrocarbons Revamp Flashcards by Shirou Aizen

What are the advantages of fossil fuels?
(Pick and roll. bruh)

Cheap, easily available
Releases lots of energy
Available 24hrs a day
” in all states of matter

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Disadvantages of fossil fuels?
(Piiiick and roooolllll)

Finite/non-renewable
Releases CO₂ (global warming)
Produces SO₂ (acid rain)

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The word eqn of combustion of alkanes?

Alkane + oxygen -> carbon dioxide + water

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Hence, symbol eqn of combustion of alkanes?
(Varies based on alkane… octane ig?)

C₈H₁₈ + 25O₂ -> 8CO₂ + 9H₂O

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What are alkanes?
(4 points)

Saturated compounds
Composed of C and H atoms
w/ σ bonds
Homologous series w/ formula C_nH_2n+2

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3 properties of alkanes?
(+ 3 small explanations)

Strong stable bonds, direct head-on overlap
Free rotation, σ bonds allow it
Non-polar molecules, C-H/C-C similar electronegativities

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Consequently, alkanes “net effect”?
(Overall outcome due to its properties)

Fairly restricted set of reactions

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What are 3 rxns u can do with alkanes?
(+ 3 small explanations)

Burn them, destroy whole molecule
React w/ halogens, break C-H bonds
Crack them, break C-C bonds

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Electronic configuration of an alkanes’ (carbon) four outermost electrons?
+ significance?

2s², 2p²
, all used in bonding

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How come all 4 electrons in carbon (alkanes) used in bonding?
(5-way)

Sp³ hybridisation
From 2s², 2p²
To 2s¹, 2p³
1 of the 2s e^- gets promoted
Now has 4 unpaired electrons

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Explain CH₄ tetrahedral shape?
(2-way)

4 Sp³ hybrid orbitals repel each other equally
Guess they 109.5° apart

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What are free radicals?
(2-way)

Atoms/groups of atoms
Having single unpaired e^-

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What type of reaction involves free radicals?

Free radical substitution reaction

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I mean… then what type of mechanism is halogenation?
(Probably optional but aye depends)

… Free radical mechanism

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How can one form free radicals?
(2-way)
Name for that?

Bond splitting evenly
Each atoms getting 1/2 electrons
Homolytic fission

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Although, what’s another term for homolytic fission?

Photochlorination

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The 3 stages of homolytic fission

Stage 1 - Initiation
Stage 2 - Propagation
Stage 3 - Termination

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Explain initiation stage… typically
(2-way)

UV radiation causes cl-cl bond (or any halogen perhaps)
to split homolytically

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Write an initiation stage example?
(Cl₂)

Cl]-[Cl -> Cl˙ + Cl˙
-> = UV
˙ dot = radical

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Explain propagation stage?
(4-way)

Radicals are very reactive
n take part in series of propagation rxns
Radical is a reactant, process will form radicals as a product
Chain reaction pretty much

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Write/”draw” a propagation stage example?
(CH₄ w/ Cl)

CH₄ + Cl˙ -> ˙CH₃ + HCl
then
˙CH₃ + Cl₂ -> CH₃Cl + ˙Cl
, there’s even a mechanism drawing here but meh.

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Explain termination stage

Propagation continues until 2 radicals meet = TERMINATION

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Write either 3 termination stage examples?

Cl˙ + Cl˙ -> Cl₂
Cl˙ + ˙CH₃ -> CH₂Cl
˙CH₃ + ˙CH₃ -> CH₃CH₃

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How are alkenes more reactive than alkanes?
(4-way)
(Careful with the explanation here… probably outdated)
(It rlly is about understanding…. ,’:D)

Alkene = C=C bond
More electron density (=bond = π and σ bond… 2 e^- pairs)
Can use that additional e^- pair to form new bonds
Alkanes break if their σ-bond is used despite already being used

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What are alkenes? (4-way)

- Unsaturated compounds - Composed of C-H & C=C bonds - w/ σ + π bonds - General formula of C_nH_{n times 2}

3 properties of alkenes? (+ 3 small explanations)

- Stronger than alkanes, the C=C bond - Restricted rotation, due to π bond - More reactive, additional e^- pair usage

What hybridisation does alkene have? + significances (5-way)

- Sp² hybridisation - 1 2s orbital + 2 2p orbitals = 3 Sp³ hybrid orbitals - Remaining unhybridised 2p orbital unchanged - Results in trigonal planar shape + σ bonding (hybridised) - and π bonding (unhybridised)

Hence, what creates the alkenes double bond? + additional significances in between (5-way)

- σ bond from head on overlap of 2 Sp₃ hybrid orbitals - strong bond holding the C_s together - π bond from sideways overlap of 2 unhybridised p orbitals - Sideways ∴ weaker - Electron density above + below plane of molecule

Draw ethene's bonds + explanation (2-way)

- Stage is yours - Due to electrons overlapping - giving rise to π bonds (or can opt for other explanation)

Due to alkenes restricted rotation, what is used to distinguish different orientations containing perhaps functional groups?

E and Z notations

E meaning in E/Z notation?

Opposite side (Entgegen)

Z meaning in E/Z notation?

"Z"ame side (Zussamen)

For E/Z notation, how to tell which is first in the name? (2-way)

- Priority rule - One with highest atomic mass

Define electrophile? (4-way)

- Atom/group of atoms attracted to - electron-rich centre/atom - Accepting pair of e^- - to form a new covalent bond

Examples of an electrophile? (Yup.)

- HBr - HCl - Cl₂ - Br₂ - H₂

Define nucleophile? (3-way)

- Chemical (don't overthink lol) - that can donate pair of e^- w/ - subsequent formation of a covalent bond

Examples of a nucleophile? (Mhm.)

- ^-OH - Br^- - Cl^- - ^-CN - H₂O - ^-NH₃

So which are susceptible to be attacked by an electrophile?

... alkenes, and only alkenes.

Hence, the mechanism for electrophiles attacking?

Electrophilic addition

What is electrophilic addition often associated with? (What is this, trivia?)

Heterolytic bond fission

What 4 things do u need for a "model" mechanism

1. Curly arrows 2. Dipoles 3. Lone pairs 4. Charges

Draw "model" mechanism of rxn between ethene and HBr

Stage is youuuurrrsss

What 2 other "addition" reactions are to of our concern?

- Bromination - Hydrogenation

Describe bromination? (1 + 2-way)

- Test for alkenes - Bromine water decolourises - if double bond present

Draw bromination mechanism (Ethene + Br₂)

Just ye lol

Describe hydrogenation? (2 things)

- 'Saturates' alkenes by adding hydrogen - Different variations of product can be produced (maybe)

Draw hydrogenation mechanism (Propene + H₂)

Go go goooo

Define carbocation? (4-way)

- Carbon atom having a positive charge - due to electron deficiency - Species highly reactive - Defined by ⊕︀

Draw reaction mechanism between HCl and propene Show which is produced in greatest quantities (2 products formed)

Bruh

From the reaction mechanism between HCl and propene, why is one produced in greatest quantities? (2-way + 2-way)

- 2° carbocations more stable than 1° - due to more alkyl groups attached - Which those donate e^- density - towards carbocation to stabilise it

Show stability of the carbocations? (From less to most)

3° > 2° > 1°

2 tests you can use for alkenes?

- Bromination - Using potassium manganate (VII)

What conditions needed to test alkenes using KMnO₄?

Must be cold. (Alkenes react if cold w/)

Difference in observations for acidified/slightly alkaline KMnO₄? (Each has the changes)

- Acidified = purple solution -> colourless - Slightly alkaline = purple solution -> dark green -> dark brown precipitate

Although, what's the jig of using KMnO₄? (1 + 3-way) (As long as it's understood)

- **May** contains carbon-carbon double bond - Equally could be any one of a - large n° of other compounds - oxidised by manganate(VII) ions under alkaline conditions

Define addition polymerisation? (3 beefy points wat)

- Addition reaction that continues until actively stopped - Monomers adding together to form long chain polymers - Only used w/ alkenes & substituted alkenes

What does a polymer not contain? and how is the name formed? (Last is 2-way)

- Doesn't actually have double bonds - By adding poly at prefix, - to involve -ene (bruh)

Draw ethene turning into polyethene

Case close it

From drawing ethene turning into polyethene, which is the monomer and which is the repeat unit?

- Monomer = ethene - Repeat unit = polyethene

What happens to ethene molecules during the formation of polyethene? [3] (1 + 2-way + 1)

- Double bond breaks - Electron pair forms new covalent bond - on a carbon from neighbouring molecule (ethene) - Forming saturated polymer chain

If u were going to draw a structural formula of a polymer, what to be aware of?

The C-C inside are actually double bonds

Great job, u know what to do

C Unit 2.5 Hydrocarbons Revamp Flashcards

(62 cards)