Hein's Flashcards (copy)

Organic chem

Hydrocarbons

Hydrocarbons

Compounds composed of only carbon and hydrogen

Alkanes

a hydrocarbon containing only single covalent bonds that form a homogenous series

Alkanes formula

CnH2n+2

Homogenous Series

a series of compounds with the same general formula, but differing form each other by a common structural unit

Cycloalkanes

single C-C bonds in a ring

3 Carbons

prop-

4 Carbons

but-

Alkane

Suffix: -ane General Formula: C(n)H(2n+2)

Alkene

Functional group: alkenyl Suffix: -ene General Formula: C(n)H(2n)

Alkyne

Functional group: Alkynyl Suffix: -yne General Formula: C(n)H(2n-12)

Alcohol

Functional group: Hydroxyl Suffix: -ol General Formula: C(n)H(2n+1)OH

ether

Functional group: ether Suffix: -oxyalkane General Formula: R-O-R'

aldehyde

Functional group: Aldehyde (carbonyl) Suffix: -anal General Formula: R-CHO

ketone

Functional group: Carbonyl Suffix: -anone General Formula: R-CO-R'

Carboxylic Acid

Functional group: Carboxyl Suffix: -anoic acid General Formula: C(n)H(2n+1)COOH

ester

Functional group: ester Suffix: -anoate General Formula: R-COO-R'

Amide

Functional group: carboxyamide Suffix: -anamide

Amine

Functional group: amine Suffix: -anamine (if more than one functional group amino infront)

Nitrile

Functional group: nitrile Suffix: -anenitrile

Arene

Functional group: Phenyl Suffix: -benzene

Phenyl

-C6H5

Halogenoalkane

addition of a halogen Name: Fluoro-, Chloro-, bromo-, iodo- General Formula: CnH(2n+1)X (where X = halogen)

Structural Isomers

Compounds with the same molecular formula but atoms and functional groups attached in different ways

• similar chemical properties

• Physical properties may differ

Primary Carbon Atom

• 1 R group

• 2 hydrogen atoms

Secondary Carbon Atom

• 2 R groups

• 1 Hydrogen atom

Tertiary Carbon Atom

• 3 R groups

• no hydrogen atoms

Benzene

C6H6

Stability of the Benzene ring

instead of creating discrete alternating π bonds the p orbital overlaps meaning the π bonds are shared by all six carbon, forming a delocalized π electron cloud which the electrons are concentrated in two donut shapes above and below the plane of the ring which is very stable

Aromatic Hydrocarbons

ring structure consisting of alternating single and double carbon-carbon bonds

Fractional Disstillation

a physical separation process that uses differences in boiling points to separate the mixture into fractions of similar boiling point.

Boiling point relative to carbon

boiling point increases as the carbon chain becomes longer

Volatility

a measure of how readily a substance vaporizes

Molar Mass affect on Volatility

Volatility increases with molar mass

Branches affect on boiling point

straight-chain isomers have stronger intermolecular forces so branched chains have a lower boiling point

Saturated Organic Compound

contains only single bonds between carbon atoms EX. Alkanes

Unsaturated Organic Compound

has at least one double or triple bond EX. Alkenes and Arenes

Aliphatics

compounds which do not contain a benzene ring, may be saturated or unsaturated EX. Alkanes and Alkenes

Arenes

compounds which contain a benzene ring, they are all unsaturated compounds EX. Benzene and Phenol

Electrophile

• an electron-deficient species which is therefore attracted to parts of molecules which are electron rich

• are positive ions or have a partial positive charge (act as a lewis acid and accept protons)

• NO2+, H+, Brδ+

Nucleophile

• an electron rich species which is therefore attracted to parts of molecules which are electron deficient

• have a lone pair of electrons and may also have a negative charge

• They act as a lewis base and donate a pair of electrons to form a new covalent bond

• Examples: Cl-, OH-, NH3, H2O, CN-

Complete Combustion of Hydrocarbons

hydrocarbon + oxygen --> carbon dioxide + water

Addition reaction

• Occurs when two reactants combine to form a single product

• Characteristic of unsaturated compounds

Substitution reaction

• occurs when one atom or group of atoms in a compound is replaced by a different atom or group

• Characteristic of saturated compounds aromatic compounds

Addition-Elimination (condensation) Reaction

• occurs when two reactions join together (addition) and in the process a small molecule such as H2O, HCl, or NH3 is lost (elimination)

• reaction occurs between functional group in each reactant

Homolytic fission

• is when a covalent bond breaks by splitting the shared pair of electrons between the two products

• produces two free radicals, each with an unpaired electron

Heterolytic fission

• is when a covalent bond breaks with both the shared electrons going to one of the products

• produces two oppositely charged ions

Leaving Group

Atoms or groups that leaves the parent chain

Incomplete combustion of hydrocarbons

occurs in unsaturated fats

Must be balanced and can be different

Mechanism for the free-radical substitution of alkanes (halogenation)

1. Initiation

2. Propagation

3. Termination

Initiation

UV light supplies the energy necessary to break the relatively week halogen bond (Ex. Cl-Cl) homolytically to form halogen free radicals (chlorine free radicals)

Propagation

1. Free radicals (Chlorine) contain an unpaired electron are very energetic so they react with an alkane (Ex. Methane) to remove a hydrogen atom forming hydrogen halogen and propagating another free radical

2. Alkane radical (Ex. Methyl Radical) reacts with another halogen to produce a halogenoalkane and another halogen radical so propagation can continue

Termination

Radical reactions can be terminated by

• Escaping from the system

• colliding with the walls

• reacting with radicals

Hydrogenation

Added: Hydrogen gas Catalyst: Nickel at 150°C Conversion: Alkene to alkane

Addition of Halogens to alkenes (Bromination)

Added: Halogen gas (Chlorine, Bromine, iodine) Catalyst: None Conversation: Alkene to dihalogenoalkane

Bromine test

Addition across a double bond. If there is double bond present in the solution, then the addition react will occur and the final solution will be completely clear. If not, the solution will remain an orange color after the bromine solution is added

Hydrohalogenation

Added: Hydrogen Halide (HCl, HBr) Catalyst: No Conversation: Alkene to halogenoalkane

HI more reactive than HBr which is more reactive than HCl

Hydration of Alkenes

Added: H2O (water) Catalyst: H2SO4 (concentrated) and steam heated Conversation: Alkene to Alcohol

Addition Polymers of Alkenes

in certain situations alkenes can break their double bond and add themselves together to produce long chains known as addition polymers which contain thousands of monomers

Combustion of Alcohols

Alcohol + oxygen --> carbon dioxide + water complete combustion

Oxidation of Primary Alcohols (Aldehyde)

Added: Potassium Dichromate (K2Cr2O7) or simply [O] Catalyst: Heated and distilled Conversation: Alcohol to Aldehyde

How does oxidation of primary alcohols to aldehyde work

• aldehydes have a lower boiling point than carboxylic acids due to their lack of hydrogen bonds which means that in a distillation column they get tapped off

Oxidation of Primary Alcohols (Carboxylic Acid)

Added: Potassium Dichromate (K2Cr2O7) or simply [O] Catalyst: Reflux Heated Conversation: Alcohol to Carboxylic acid Color Change: orange to green

How does oxidation of primary alcohols to carboxylic acid work

By refluxing to expose the aldehyde to the oxidizing agent for a prolonged period of time

refluxing

is a technique that involves the cyclic evaporation and condensation of a volatile reaction mixture, preserving the solvent as it does not evaporate

Oxidation of Secondary alcohols

Added: Potassium Dichromate (K2Cr2O7) or simply [O] Catalyst: Reflux Heated Conversation: Alcohol to ketone (2 H atoms removed) Color Change: orange to green

Oxidation of Tertiary alcohols

no reaction so no color change as it would involve the breaking of the carbon skeleton which requires significantly more energy

Esterification

Added: Carboxylic acid Catalyst: Concentrated H2SO4 (Sulfuric acid) Conversation: Alcohol to ester

Halogenoalkanes reactivity

with the exception of fluoroalkanes halogenoalkanes are more reactive than alkanes as the carbon and halogen bond is weaker than C-C and C-H, but do not burn as readily

Nucleophilic substitution of halogenoalkanes

carbon-halogen bond is polar so the electron deficient carbon is open to be attacked by a nucleophile

Chemical Reactivity of Benzene

does not readily undergo addition reactions as an additional 150 kJ mol^-1 of energy is required to overcome the delocalization energy, but electron deficient species which are electrophiles (positive or slightly positive (δ+)) are attracted to the electron above and below the ring, thus substituting a hydrogen atom

Benzene with Nitric acid

Added: Nitric acid (HNO3) Catalyst: Concentrated H2SO4 (Sulfuric acid) and heat Conversation: New aromat and water

Benzene with bromine

Added: Br2 Catalyst: Aluminium Tribromide (AlBr3) Conversation: New aromat and Hyrdogen halide

Electronegativity Table

Nucleophilic substitution

A type of substitution reaction in which a nucleophile is attracted to an electron-deficient centre or atom, where it donates a pair of electrons to form a new covalent bond.

Rate of reaction of Primary Halogenoalkanes

depends on the concentration of the halogenoalkane and the nucleophile

Rate of reaction of Tertiary Halogenoalkanes

depends only on the concentration of the halogenoalkane

Nucleophilic Substitution of Primary Halogenoalkanes

an Sn2 mechanism

Sn2

• substitution nucleophilic bimolecular

• 1 step

• 2 molecules in the rate determining step

• primary alcohol

inversion of configuration (Walden inversion)

when a nucleophile attacks the electron deficient carbon from the opposite side of the leaving group

Drawing mechanisms for Sn2 reactions

1. curly arrow from nucleophiles lone pair of negative charge terminating at the carbon atom

2. curly arrow from the bond between the carbon and halogen, ending at the halogen (leaving group)

3. Partial bonds represented by dotted lines make up the transition state which is enclosed by square brackets with a single negative charge

4. Formation of product and leaving group shown

Steric Hindrance

large bulky groups prevent the mobility of a nucleophile

Nucleophilic Substitution of a tertiary Halogenoalkanes

an Sn1 mechanism

Step 1: Heterolytic breaking of the carbon-halogen bond creating a halide ion and a carbocation intermediate Step 2: Nucleophile attaches to the carbocation

Inductive effect

Electron donation or withdrawal through the sigma bonds of a molecule.

Stability of Carbocations

drawing mechanisms for Sn1 reactions

1. curly arrow from carbon-halogen bond to the halogen leaving group

2. representation of the carbocation which clearly shows a positively charged central carbon atom

3. curly arrow from the nucleophiles lone electron pair or negative charge, terminating at the carbon atom

4. formation of the product and leaving group must be shown

What type of nucleophilic substitution do secondary halogenoalkanes undergo

both Sn2 and Sn1

Factors affecting the rate of nucleophilic substitution

1. Type of halogenoalkane

2. Nature of the halogen

3. Choice of Solvent

Type of Halogenoalkane affect on the rate of nucleophilic substitution

Tertiary > Secondary > Primary

Nature of the Halogen affect on the rate of nucleophilic substitution

C-I bond is weaker than the C-Br bond which is in-turn weaker than the C-Cl bond, so iodine is a better leaving group as less energy is required and it occurs faster

Choice of Solvent affect on the rate of nucleophilic substitution

• Sn2 reactions favor aprotic, polar solvents

• Sn1 reactions favor protic, polar solvents

Why do Sn2 reactions favor aprotic, polar solvents

• don't possess OH or NH group so they can't for a hydrogen bond with the nucleophile

• Doesn't solvate the nucleophile allowing it to maintain its properties

Why do Sn1 reactions favor protic, polar solvents

• are polar

• possess an OH or NH group so they can for a hydrogen bond with the nucleophile

• solvates the nucleophile allowing it to attack electrophiles such as the δ+ carbon

Aprotic

does not contain a hydrogen ion

Protic

contains a hydrogen ion

Solvation

process by which solvent molecules surround the dissolved ions

What makes a good nucleophile?

• strong charge

• negatively charged particles (OH-) are better nucleophiles than polar substances (H2O)

Why do alkenes attract nucleophiles

alkenes contain an electron cloud, created by the pi bond 90° to the plane of the sigma bonds, which is attracts electrophiles

electrophilic addition reactions

Addition of an electrophile to a carbon-carbon double bond to yield a saturated product

Drawing mechanisms for electrophilic addition reactions

1. curly arrow from carbon-carbon bond to the positive section

2. curly arrow from the bond in the added substance ending in negative section

3. curly arrow from lone pair or negative charge to C+ (carbocation)

4. Structural formula shown of product

Electrophilic addition of halogens to alkenes

as the halogen approaches the electron rich C=C bond of the alkene electrons within the halogen molecule are repelled, resulting in a temporary dipole