Alkanes And Cycloalkanes Flashcards
What are hydrocarbons
Compounds composed entirely of carbon and hydrogen
What are the major classes of hydrocarbons?
Alkanes, alkenes, alkynes, and aromatic hydrocarbons
A hydrocarbon with no double or triple bonds is said to be?
Saturated
What is the general formula of alkanes?
CnH2n+2
What is the shape and hybridization of all the carbon atoms in an alkane?
Sp3 hybridization, tetrahedral in shape
Why are alkanes unreactive to most chemical reagents?
Because of strong sigma bonds
What are alkanes sometimes referred to as?
Straight chain or acyclic alkanes to distinguish them from cycloalkane or alicyclic compounds
What are alkanes primarily used as?
Fuels, solvents, and lubricants
What are natural gas, gasoline, kerosene, heating oil, lubricating oil, and paraffin wax composed of?
Of alkanes with different physical properties resulting from different ranger of molecular weights
Alkanes are polar or non-polar?
Nonpolar
Why are alkanes good lubricants and preservatives for metals?
They keep water from reaching the metal surface and causing corrosion
What are cycloalkanes?
Alkanes that contain rings of carbon atoms
Are most cycloalkanes reactive or unreactive?
Unreactive
What was cyclopropane used once as?
General anesthetic because its vapors cause sleepiness and a loss of consciousness
How did cyclopropane act like an anesthetic?
After inhalation into the lungs, cyclopropane goes into the blood
Due to its non polar nature, it rapidly leaves the blood and passes through the non polar membranes surrounding the central nervous system, where it produces anesthesia
Why is cyclopropane no longer used as an anesthetic?
Highly flammable and can cause explosions when mixed with air
What is the primary source of alkanes?
Natural gas and petroleum
What does natural gas mainly contain?
Methane
Propane and butane are common fuels in what?
In propone gas burners and cigarette lighters
Alkanes with 5 to 8 carbons are what?
Gasoline
Alkanes with 9 to 16 carbons are what?
Diesel
As the number of carbons increase the boiling point and viscosity…
Increases
What does IUPAC stand for?
International Union of pure and applied chemistry
What is a property of sigma bonds in alkanes?
The bond keeps rotating
what does the rotation of the bond result in?
different spatial arrangement of hydrogen atoms in the molecule
What are conformations?
The different spatial arrangement of the atoms/groups that result from the single bond rotation
What are molecules with different conformations called?
conformers or conformational isomers
What is staggered conformation?
All of the h atoms spread out
What is eclipsed conformation?
All of the h atoms overlapped
What is anti conformation?
Most stable staggered conformation
When the largest groups on the front and rear carbon are 180° opposite to each other it is called?
Anti conformations
When the two large groups are adjacent and are 60° to each other it is called?
Gauche conformation
Which is the most stable cycloalkane?
Cyclohexane
What is the most stable conformation of cyclohexane?
Chair conformation
In the chair conformation of cyclohexane the total twelve c-h bonds can be divided into what two categories?
Axial → upward
Equatorial → downward
What are the methods for preparation of the alkanes?
Laboratory method
From Grignard’s reagent
what is the laboratory method?
The laboratory preparation of methane is done by heating sodium acetate in the presence of soda lime in a test tube
On heating, methane gas is formed due to elimination of Co2
How are alkanes prepared from Gringard’S reagent?
Gringard’s reagent with water or dilute acid decomposes to alkanes
What are the chemical reactions of alkanes?
Combustion
Halogenation
Cracking process
Hydrocracking
What is combustion?
Rapid oxidation that takes place at high temperature converting alkanes to carbon dioxide and water
What is halogenation?
Alkanes reacting with halogens to form alkyl halides
What is cracking process?
Operates under conditions that give the maximum yield of gasoline
Without hydrogen giving a mixture of alkanes and alkenes
What is hydrocracking?
Hydrogen is added to give saturated hydrocarbons
