#3: Alknenes and Cycloalkenes Flashcards
aliphatic hydrocarbons whose molecules contain double-bond carbon-carbon atom.
alkenes
the old name of alkenes that is still often used
olefins
the simplest olefin (alkene), was called olefiant gas
Ethene (ethelene)
- the lowest form of alkene is planar angles between bonds are 120 degrees
-It is sp2 hybrid Orbital
ethene
The molecular formula of alkenes
CnH2n
is an orbital formed by the linear combination of one s and two p orbitals of comparable energy (such 2s and 2p orbitals) on the same atom.
sp2 orbital
covalent chemical bonds, in each of which two lobes of an orbital on one atom overlap with two lobes of an orbital on another atom, and in which this overlap occurs laterally.
pi bond
Covalent bonds are formed by the ______ of atomic orbitals.
overlapping
a result of the head-to-head overlapping of atomic orbitals
sigma bond
what kind of bond is a single carbon-carbon bond
sigma bond
- If more than one double bond is present, indicate their position by using the number of the first carbon of each double bond and use the suffix ____ (for 2 double bonds), _____ (for 3 double bonds), and _____ (for 4 double bonds)
-diene; -triene; tetraene
alkenes have a double bond at the end of the carbon chain.
terminal alkenes
have at least one carbon atom bonded to
end of the double bond.
internal alkenes
A carbon-carbon triple bond consists of ____ and _____
one sigma bond; two π bonds
contain a double bond in a ring.
cycloalkenes
Alkenes are ____ than water and are _____ in water due to their ____ characteristics. Alkenes are only ____ in nonpolar solvents.
less dense; insoluble; non-polar; soluble
Alkenes are prepared (synthesized) industrially by ____ of petroleum.
thermal cracking
a reaction that literally cracks or breaks alkane into smaller ones.
cracking
alkenes can be prepared from alkyl halides and alcohols via ____.
elimination reactions
a plant hormone that induces ripening of fruits.
ethene
a reaction in alkenes where the π bond is broken and two new σ bonds are formed.
addition reaction
Alkenes are _____, with the electron density of the π bond concentrated above and below the plane of the molecule.
electron-rich
Alkenes react with ____.
electrophiles
takes place when both X and Y are added from the same side.
syn addition
takes place when X and Y are added from opposite sides
anti addition
Most alkene addition reactions are _____–the products are more stable (lower in energy) than the reactants.
exothermic
Addition of HX (HCl, HBr, or HI) to an alkene gives a ____.
haloalkane
process that favors bond formation at a particular atom over other possible atoms
regioselective
states that, in hydrohalogenation of an unsymmetrical alkene, the hydrogen atom in the hydrogen halide forms a bond with the doubly bonded carbon atom in the alkene, bearing the greater number of hydrogen atoms.
Markovnikov’s rule
Addition of water is called
hydration
hydration is ____, usually by H2SO4
acid-catalyzed
Virtually all alkenes add H2 in the presence of a transition metal catalyst, commonly ____
- platinum
-palladium - nickel
Due to the presence of carbon-carbon multiple bonds, alkenes, and alkynes are very susceptible to ____.
oxidation
If the potassium manganate(VII) solution is acidified with dilute sulfuric acid, the purple solution becomes _____.
colorless
If the potassium manganate(VII) solution is made slightly alkaline (often by adding sodium carbonate solution), the purple solution first becomes dark green and then produces a _____ precipitate.
dark brown
KMnO4 is a
Baeyer’s reagent
- used to detect the presence of unsaturation in a molecule.
- the decolorization of the purple color of KMnO4 and the formation of a brown precipitate.
Baeyer’s Test: Hydroxylation
The formation of glycol may be a prelude to the eventual cleavage of the double bond. When this happens, oxidation is classified as the _____.
oxidative cleavage
Alkene oxidative cleavage occurs when the alkene is reacted with
- hot KMnO4
- O3 followed by H2O and Zn (ozonolysis)
The products formed from oxidative cleavage
aldehydes, ketones, carbon dioxide, or acids
A terminal doubly-bonded carbon atom that contains two hydrogen atoms is cleaved by hot KMnO4 to form CO2 and by ozonolysis to form _____.
formaldehyde
substances having a general formula of CnH2n, also known as unsaturated HC.
It is composed of a double bond structure which has an angle of 120 degrees. One bond is sigma and the other one is called pi bond.
alkenes
alkenes exhibit isomerism where the functional group and its position are the same but the carbon skeleton is different.
skeletal isomerism
differs in the position of the functional group.
positional isomerism
its double-bond alkene can have cis and trans isomerism.
geometrical isomerism
The addition of hydrogen to alkenes may lead to the production of _____
alkanes
