Basic organic chem key points flashcards

Define homologous series

Series of organic compounds with the same functional group but each successive member differing by CH2

Define functional group

Part of organic molecule that is responsible for its chemical reactions

Define alkyl group

Part of organic molecule with the general formula CnH2n+1

General formula alkane, alkene, alcohol

Alkane - CnH2n+2

Alkene - CnH2n

Alcohol - CnH2n+1OH

Define structural isomer

Compounds with the same molecular formula but with different structural formulae

What bombs do alkanes and alkenes contain?

Alkanes - C—C all single covalent sigma bonds

Alkenes - C=C double covalent bond contains one sigma bond and one pi bond. C—H all single covalent sigma bonds

Trend in boiling point as alkane chain length increases?

B. P. Increases because longer molecules have more points of surface contact and stronger London forces. Therefore more heat energy is needed to break the intermolecular forces between the molecules

Trend in B. P. As alkane branching increases?

B. P. Decreases because more branched molecules have less points of surface contact and weaker London forces. Therefore less heat energy is needed to break the intermolecular forces between the molecules

Name reaction - alkane + halogen

Radical substitution

Conditions — alkane + halogen

UV radiation

Define radical

Species with unpaired outer electron

Define homolytic fission

Breaking of covalent bond in the formation of two radicals due to an equal split of the electron pair

Define heterolytic fission

Breaking of a covalent bond that results in the formation of a positive and negative ion due to an unequal split of the electron pair

Initiation, propagation, and termination equations - methane + bromine

Initiation — Br2 → 2BR•

Propagation CH4 + Br• → CH3 + HBr

CH• + Br2 → CH3Br + Br•

Termination CH3• + CH3• → C2H6

CH3• + Br• → CH3Br

Br• + Br• → Br2

Overall equation reaction methane + bromine

CH4 +Br2 → CH3Br + HBr

Describe what happens in initiation, propagation, and termination

Initiation — the halogen is split into 2 halogen radicals

Propagation — 1. A halogen radical reacts with the alkane to form an alkaline radical and a hydrogen halogen 2. The alkyl radical reacts with the halogen to form a haloalkane and reform the halogen radical

Termination — any pair of radicals react together tp form halogen, haloalkane, or alkane

Define curly arrow

Movement of a pair of electrons showing bonds made / broken

Why is it difficult to produce a specific product in a radical substitution?

Substitutions can occur at any carbon atom on the chain, multiple substitutions can occur forming haloalkanes with more than one halogen atom

Describe the formation of the C=C double bond

The sigma bond is formed by a direct overlap between two orbitals. The pi bond is formed by a sideways overlap of two p orbitals above and below the plane of the molecule.

Why are alkenes reactive?

The pi bond is much weaker than the sigma bond and easier to break.

What reaction do alkenes undergo?

Electrophilic addition

Define electrophile

Species that is an electron pair acceptor

Name examples of electrophiles.

Halogens, water (steam), hydrogen, hydrogen halides

What is Markovnikovs rule?

A most stable carbocation is more likely to be formed during electrophilic addition. The hydrogen atom will bond with the carbon that has the most hydrogens already bonded to it.

Describe steps in in electrophilic addition mechanism

1. Curly arrow from double bond to delta positive atom.

2. Curly arrow from electrophile bond to delta negative atom.

3. Draw the carbocation and the negative ion.

4. Draw a curly arrow from the lone pair on the negative ion to the positive carbon in the carbocation

5. Draw the final product (alkane, alcohol, haloalkane)

What is the overall equation for the reaction of but-2-ene + iodine

CH3CHCHCH3 + I2 → CH3CHICHICH3

Define stereoisomer

Compounds with the same structural formula but with a different arrangement of atoms in space

When does E/Z isomerism arise?

Each carbon atom in C=C double bond is attached to two different groups

What determines if an isomer is E/Z?

E isomer-higher priority groups are on opposite sides of the double bond Z isomer - higher priority groups are on same side of the double bond

Why does but-1-ene not show E/Z isomerism?

The first carbon in the double bond is attached to two hydrogen atoms (both groups attached are the same).