STPM Chemistry Topic 14 Carbon Chemistry (Short notes)

Topic 14: Carbon Chemistry

SMK SACRED HEART, SIBU

Tetravalent Small Size 1. Carbon forms organic compound HCH3 Catenate RCH3 % by mass , Mass of CO2 and H2O R2CH2 Empirical Formula Empirical F, Combustion analysis R3CH Molecular Formula 2. Chemical formula Displayed , Condensed , Skeletal R4C Structural Formula R C and C+ Stability: 3o > 2o > 1o > CH3 E+ = Lewis acid 3. Carbon species − − Nu = Lewis base C Stability: 3o < 2o < 1o < CH3

is is is is is

1oC 1oC 2oC 3oC 4oC

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Chain Position Functional Group

Structural

Change in Carbon skeleton Change in position of functional group (a) Alkene Alkene & Cycloalk Cycloalkane ane (b) Alcohol Alcohol & Ether Ether (c) Aldehyde Aldehyde & Keton Ketone e (d) Carbocylic Carbocylic acid acid & Ester Ester trans

cis

4. Isomerism Geometrical Higher m/p Closely pack Symmertical VDWF

Stereoisomerism

Higher b/p More polar

Optical Positive Inductive effect

EWG increases acid strength / decreases pKa Eg: Phenyl group, Hydroxyl group, Nitro- group ↑ when

Negative

no. of EDG ↑ / Size of alkyl group ↑ / Distance ↓

EDG decreases acid strength / decreases Eg: alkyl group and cycloalkyl group

pKb

↑ when

5. Acid/Base Strength

Resonance effect

no. of EWG ↑ / Electronegativity ↑ / Distance ↓ Formation of more stable RCOO - , C6H5O - , C6H5NH2 Eg: RCOOH + H2O ⇋ RCOO – + H3O+ Equilibrium shift to right

Increasing acid acid strength : ROH < H 2O < phenol < RCOOH < Benzoic acid 6. EDG/EWG eg: -OH

Attached to benzene ring (-OH is EDG) Not attached to benzene ring (-OH is EWG)

Resonance

Inductive effect

Electron from O delocalises into benzene ring Increases acid strength