organic I Flashcards by Sim Kaur

What is a homologous series?

A series of compounds with the same functional group and general formula, differing by CH₂.

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Define structural isomerism.

Compounds with the same molecular formula but different structural formulae.

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Name the three types of structural isomers.

Chain, position, and functional group isomers.

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What is stereoisomerism?

Same structural formula, different spatial arrangement.

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What is E/Z (geometrical) isomerism?

Type of stereoisomerism due to restricted rotation about C=C and two different groups on each C.

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General formula of alkanes?

CnH2n+2

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What type of bonding is in alkanes?

Sigma (σ) bonds only — single covalent bonds.

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What is complete combustion of an alkane?

CxHy + O2 → CO2 + H2O

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What is incomplete combustion?

Occurs with limited oxygen: produces CO or C.

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What is the mechanism for the reaction of alkanes with halogens?

Free radical substitution (initiation, propagation, termination).

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Equation for initiation step in CH₄ + Cl₂?

Cl2 → 2Cl⋅ (under UV light)

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What is fractional distillation?

Separation of crude oil into fractions by boiling point.

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What is cracking?

Breaking long-chain hydrocarbons into shorter alkanes and alkenes.

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Give an equation for thermal cracking.

C10H22 → C8H18 + C2H4

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What conditions are used in catalytic cracking?

Zeolite catalyst, 450°C, slight pressure.

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General formula of alkenes?

CnH2n

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What type of bonds are in alkenes?

One sigma (σ) bond and one pi (π) bond in the C=C.

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Mechanism for alkenes + HBr?

Electrophilic addition.

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Equation for alkene + hydrogen?

C2H4 + H2 → C2H6 (Nickel catalyst, 150°C)

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What is Markovnikov’s Rule?

In unsymmetrical alkenes, the hydrogen adds to the carbon with more hydrogens already attached.

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Test for alkenes?

Bromine water: orange → colourless.

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What is addition polymerisation?

Repeating addition of monomers with C=C to form long-chain polymers.

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Monomer of poly(ethene)?

Ethene

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General formula of haloalkanes?

CnH2n+1X

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What type of mechanism do haloalkanes undergo with nucleophiles?

Nucleophilic substitution.

Give an equation: CH₃Cl + OH⁻ → ?

CH3Cl + OH− → CH3OH + Cl−

What nucleophiles can attack haloalkanes?

OH⁻, CN⁻, NH₃

What is the trend in reactivity of haloalkanes?

Increases down the group (C–I bond is weaker).

What happens in elimination with OH⁻ in ethanol?

Alkene forms: CH3CH2Br + OH− → CH2=CH2 + H2O + Br−

General formula of alcohols?

CnH2n+1OH

What is a primary alcohol?

–OH group attached to a carbon with one alkyl group.

How do you oxidise a primary alcohol?

Gently: → aldehyde; Reflux: → carboxylic acid (Use acidified K₂Cr₂O₇)

What is observed during oxidation with K₂Cr₂O₇?

Orange → green

Equation for ethanol to ethanal?

CH3CH2OH + [O] → CH3CHO + H2O

Equation for ethanol to ethanoic acid?

CH3CH2OH + 2[O] → CH3COOH + H2O

Dehydration of alcohols produces?

Alkenes (elimination): CH3CH2OH → H2SO4 CH2=CH2 + H2O

Conditions for fermentation?

Yeast, 30–40°C, anaerobic

Equation for fermentation of glucose?

C6H12O6 → 2C2H5OH + 2CO2

Conditions for hydration of ethene?

Steam, phosphoric acid catalyst, 300°C, 60 atm

What does IR spectroscopy measure?

Absorption of IR radiation by covalent bonds in molecules.

What is the fingerprint region?

Area below 1500 cm⁻¹ unique to each compound.

Typical absorption: O–H alcohol stretch?

Broad peak at 3200–3600 cm⁻¹

Typical absorption: C=O stretch?

Sharp peak near 1700 cm⁻¹

What does the molecular ion peak (M⁺) indicate?

The molecular mass of the compound.

What are fragments in a mass spectrum?

Pieces of the molecule formed during ionisation.

Explain how the structure of E/Z isomers arises. (2 marks)

Due to restricted rotation around C=C and two different groups attached to each carbon.

Describe the mechanism for the reaction of ethene with HBr. (4 marks)

Electrophilic addition: H⁺ attacks C=C, carbocation forms, Br⁻ adds to carbocation.

Describe a test to distinguish between an alkane and an alkene. (2 marks)

Add bromine water: alkene decolourises it; alkane does not.

A student refluxes butan-1-ol with acidified potassium dichromate. What is the organic product? (1 mark)

Butanoic acid

How can ethanol be produced industrially? (2 marks)

Hydration of ethene with steam and phosphoric acid catalyst.

What is the IUPAC name for CH₃CH₂CH₂OH?

Propan-1-ol

What is the suffix for a ketone?

-one (e.g. propanone)

What is the prefix used for a halogenoalkane?

fluoro-, chloro-, bromo-, iodo-

How do you number the chain for naming?

From the end giving the lowest possible numbers to substituents.

What is the test for carboxylic acids?

Add NaHCO₃ → effervescence of CO₂.

What is the test for an aldehyde?

Tollens' reagent: silver mirror forms.

What is the test for a ketone?

Tollens’ gives no visible reaction.

What is the test for alcohols?

Add Na → effervescence (H₂), or K₂Cr₂O₇/H⁺ → colour change with primary/secondary.

What is the test for a halogenoalkane?

Add NaOH, warm → acidify → add AgNO₃: Cl⁻ white ppt, Br⁻ cream ppt, I⁻ yellow ppt.

Write the equation for the complete combustion of ethanol.

C2H5OH + 3O2 → 2CO2 + 3H2O

Explain why tertiary alcohols do not oxidise easily. (1 mark)

No hydrogen attached to the carbon with the OH group.

Describe how you would convert ethanol into ethene. (3 marks)

Reagent: conc. H₂SO₄ or Al₂O₃; Conditions: Heat; Mechanism: Elimination.

Compare industrial hydration vs fermentation of ethanol (4 marks)

Hydration: fast, continuous, pure product, non-renewable; Fermentation: slow, batch, impure, renewable.

What are the conditions and mechanism for the reaction: alkene → alkane?

Reagent: H₂; Conditions: Ni catalyst, 150°C; Mechanism: Electrophilic addition.

What are the conditions and mechanism for the reaction: alkene → dibromoalkane?

Reagent: Br₂; Conditions: Room temperature; Mechanism: Electrophilic addition.

What are the conditions and mechanism for the reaction: alkene → alcohol (via steam)?

Reagent: Steam (H₂O); Conditions: H₃PO₄ catalyst, 300°C, 60 atm; Mechanism: Electrophilic addition.

What are the conditions and mechanism for the reaction: haloalkane → alcohol?

Reagent: Aqueous NaOH; Conditions: Warm; Mechanism: Nucleophilic substitution.

What are the conditions and mechanism for the reaction: haloalkane → nitrile?

Reagent: KCN in ethanol; Conditions: Reflux; Mechanism: Nucleophilic substitution.

What are the conditions and mechanism for the reaction: alcohol → alkene?

Reagent: Conc. H₂SO₄ or Al₂O₃; Conditions: Heat; Mechanism: Elimination.

What are the conditions and mechanism for the reaction: primary alcohol → aldehyde?

Reagent: K₂Cr₂O₇/H⁺; Conditions: Distillation; Mechanism: Oxidation.

What are the conditions and mechanism for the reaction: primary alcohol → carboxylic acid?

Reagent: K₂Cr₂O₇/H⁺; Conditions: Reflux; Mechanism: Oxidation.

how do you name the product from potassium cyanide elimination reactions?

name ends in nitrile (one extra carbon from :CN- is added btw) e.g: propanEnitrile *don't forget the E

how many steps are in nucleophilic substitution mechanisms?

usually 1 step, but for NH3 it is 4 (like alcohols and alkenes one)

how many steps are in alcohol and alkene mechanisms?

4 (don't forget: O+ bit in H-O-H step)

what are primary alcohols oxidised to?

aldehydes, and can be further to carboxylic acids too

what are secondary alcohols oxidised to?

ketones

what are tertiary alcohols oxidised to?

they are not

reflux is used for what?

to produce carboxylic acid FROM alcohols (and ketones too)

how are aldehydes formed?

from fractional distillation of alcohols

reagent in distillation of alcohol? and condition?

reagent = conc phosphoric/sulfuric acid condition = hot temp

test for alcohols? and positive result?

acidified potassium dichromate colour change from orange TO green

what bonds form between alcohols molecules?

hydrogen bondsh

hydration of any alcohol (e.g. ethene) equation? and conditions?

C2H4 (g) + H2O(g) --> C2H5OH (l) at 300 degrees C and 60 ATM using solid phosphoric acid catalyst

equation and conditions for fermentation?

C6H12O6 --> 2C2H5OH + 2CO2 yeast, anaerobic, 30-40 degrees C temp (38 = optimal for yeast enzymes)

one downside to fermentation method?

costly as requires fractional distillation for purification

pros (2) and cons (2) of biofuel usage

+ renewable + lower net CO2 emissions - engine modifications - competition for land

what equations can be used to show ethanol from fermentation as carbon neutral?

photosynthesis, fermentation and combustion doesn't take into consideration fuel burned for transportation etc

organic I Flashcards

(87 cards)