Alkanes , Cycloalkanes and Alkyl Halides Flashcards
Saturated Hydrocarbons
Only hydrogens and sp3 hybridised carbons
n-alkanes
Chains of -CH2- groups (methylene groups),
Branched alkanes
Structural isomers of n-alkanes
equation for hydrogens in carbon atoms
(2n + 2) hydrogen atoms
Non-polar molecules
Dissolve in non-polar or weakly polar organic solvents and are hydrophobic
Less dense than water and insoluble in water
Which bond does rotation occour?
In single bonds not double
Conformational isomer
- Formed due to rotation of carbon sp3
What energy conformation are structures usually drawn in?
- Lowest-energy conformation: the one with
minimal electrostatic repulsion between bonds - Bonds are usually 120 degrees appart (Rotation at 120)
- Stable conformation
High energy conformation
- Rotation at 60 degrees
- Looking at newmans projection the front hydrogens and inm the same plane as back 9eclipse and repel at first rotation
- Torsional strain
what energy does the staggered formation have
- Lowest relative energy at angle 60 280 and 300 dihedral angle
Gauche
- 1st staggered level it is synclinical
- 2 biggest substituent next to each other
Opposed
- No eclipses are with large molecules
Cycloalkane
- open-chain alkanes in their physical properties
and in their chemistry
Cis
Two substituents point toward the same face
trans
Two substituents point toward opposite face
Torsional strain
- Chair conformation is required due to strain not flat but staggered
- 109.5 degree angle
Cyclohexane conformational equalibria chair
- Lowest energy all hydryogen as far appart as posible to avoid tortional strain
Chain formation structure
Axial substituentdrawn vertically
Equatorial drawn parallel to the next but-one C-C bond
Does cyclohexane prefer equatorial or axial
- Prefer to stay in equatorial less interaction between substituents
Larger substituents give a greater preference to
- Equatorial position
Alkyl halides
Halogen atom bonded to one of the sp3 hybrid atoms
Vinyl halide
Halide bonded from carbon double bond
Aryl halide
- Benzene with halide bonded
Nucleophiles
- Wish to form bonds by donating or sharing their electrons
- electrons rich and can be negative ions, or neutral molecules with electron lone pairs
Electrophiles
- Wish to form bonds by accepting electrons or
sharing electrons with a reactant molecule
electron deficient and can be positive ions or neutral (but δ+) molecules
Nucleophilic substitution
- Replaces a leaving group (X−) from a
carbon atom, using its lone pair of electrons to form a new bond to the carbon atom
Elimination reaction
- Halide ion leaves along with another atom or ion (often H+), a
new pi bond results. Dehydrohalogenations (H-X). Reagent (B:-) reacts as a base. - Most nucleophiles are also basic
Where do the curly arrows go
- Nucleophil eto electrophile
- movement of electrons
