HC: Alkanes only

Hydrocarbons

organic compounds composed entirely of carbon (C) and hydrogen (H) atoms, serving as the primary components of fossil fuels like petroleum and natural gas.

Alkanes

Paraffin

Alkenes

Olefins

Alkynes

Acetylenes

parum affinis

little or low affinity/ reactivity (alkanes)

CnH2n

gen. formula for cyclic hc

CnH2n+2

gen. formula for acyclic hc

true or false: alkanes are non-polar

true

aliphatic structure

straight, chain, branched, non-aromatic; alkanes, alkenes, alkynes

aromatic structure

contains benzene ring or benzene with alternating double bonds; very stable (due to resonance)

saturated bonds

all single bonds only

unsaturated bonds

can be double or triple bonds

heterocyclic aromatic structure/ compounds

cyclic structures in which the ring atoms may include oxygen or nitrogen while maintaining the special stability of aromaticity

cyclic structure

carbons are connected in a ring (closed chain)

hexane

an alkane obtained from crude oil during petroleum refining

fractional distillation

method used in petroleum refining

crude oil

mixt. of hydrocarbons (many of these are alkanes)

distillation

process to separate components of a liquid mixture based on their boiling points differences through evaporation and condensation.

fractional distillation

type of distillation used to separate a mixture into many components based on close boiling points difference

simple distillation

type of distillation used to separate a mixture into many components based on large boiling points difference

fractionating column

vertical tube that helps separate liquids based on their boiling points by repeated vaporization and condensation.

great IMF, more energy, and high temp/ low boiling point

required to break longer chains

weak IMF, less energy, and low temp/ low boiling point

required to break shorter chains

78.3°C

boiling point of ethanol

100°C

boiling point of water

plates/ trays

horizontal structures inside a fractionating column where vapors condense and liquids are collected during separation.

methane

compound collected as gas (refinery gas) and has low boiling point

hexane

liquid fraction (gasoline range) and has low boiling point

1-4 Carbons

alkane is gas

5-17 Carbons

alkane is a colorless liquid

18 and more Carbons

alkane is a waxy/ white solid, a paraffin wax, or white candles

less dense will...

more dense will…

sink

isomerism

same molecular formula but different structure

alkanes should have…

skeletal isomerism

1° Primary, 2° Secondary, 3° Tertiary, and 4° Quaternary

types of carbon

1° primary carbon

only 1 carbon is attached

2° secondary carbon

only 2 carbon is attached

3° tertiary carbon

only 3 carbon is attached

4° primary carbon

only 4 carbon is attached

stereoisomers

same connectivity but different spatial arrangements

stereochemistry

study of 3D arrangement of atoms in molecules and how this affects their properties

Conformational Isomers (conformers)

arrangement of the atoms in 3d; due to rotation around single bonds; no bonds are broken

Configuration

fixed 3d arrangement (no easy rotation)

1. Sawhorse Representation

2. Newman Projection

3. Staggered Conformation

4. Eclipsed Conformation

5. Gauche Conformation

6. Anti-conformation

6 ways to show conformations

sawhorse representation

bonds are slightly tilted and molecules are slanted in 3d view

newman projection

looking directly along a C-C bond wherein front carbon and back carbon exists.

torsional strain

repulsion between bonds because they are too closed/ aligned (in eclipsed conformation)

steric strain

repulsion b/w atoms/ groups due to crowding in space.

dihedral angle

angle between bonds on the front carbon and bonds on the back carbon

eclipsed and staggered conformation

2 types of newman projection

eclipsed conformation

0° dihedral angle

eclipsed conformation

bonds are perfectly aligned and with highest torsional strain

staggered conformation

can be gauche or anti-conformation

staggered conformation

bonds are not aligned, more relaxed and less energy

gauche conformation

bonds are 60° apart from each other; has slight steric strain

anti-conformation

groups are 180° apart from each other; most stable=no steric and torsional strain = lowest energy

staggered-gauche conformation

sawhorse representation

anti-conformation

polymorphism

ability of a compound to exist in >1 crystal form

halogen substituents

fluoro, chloro, bromo, iodo

group 17

group # of halogens in the periodic table

haloalkane

adding halogen to an alkane

109.5°, tetrahedral angle

cycloalkanes ideal angle

cyclopentane/ envelope

most stable cycloalkane

chair > twist-boat > boat

stability order of cyclohexane conformations

cis-trans isomers

refers to stereoisomerism in which substituents on a ring are either on the same side (cis) or opposite side (trans) of the ring plane.

cis isomer

subst. on same side

trans isomer

subst. on opposite side

1. oxidation/ combustion and

2. halogenation

the two alkane rxns

combustion

an oxidation rxn that produces flame

complete and incomplete

two types of combustion

complete rxn

happens when there is enough Oxygen (O2)

production of carbon dioxide and water

incomplete rxn

happens when oxygen is limited

products: carbon monoxide and soot

can be cancer-causing (halogenation)

alkanes will not react unless there is a catalyst

soot

black sticky carbon leftover

chloroform (CHCl3) and carbon tetrachloride (CCl4)

carcinogenic compounds

catalyst

speeds up a reaction (ex. UV light/ heat)

cleaving

breaking a chemical bond.

uses curved line to cut an atom away

2-3-dimethylpentane

6-bromo-2-chloro-3-methylheptane

3-ethyl-2-methylhexane

1-ethyl-2,4-dimethylcyclohexane