FoC : Organic Structures And Mechanisms Flashcards
Definition: isomer
Compounds with the same molecular formula but different constitution, configuration and conformation
Definition: Constitutional isomers
Differences in the nature of sequence of atoms in a molecule (connectivity)
Definition: stereoisomer
Two or more compounds whose structure differ only I. The 3d arrangement of their constituent atoms. (Same constituency but fixed in different special arrangement)
Why is their stereo isomerism in alkenes (sp2 carbon)
Alkenes are planar
Double bond (pi and sigma)
No rotation as would break pi overlap
These are isolatable, separatable with different boiling points and optical properties
How is priority assigned in a stereoisomer
Atomic number
Oxidation level
Why is there steroisomerism in saturated carbons (sp3 carbons)
If 4 different groups are attached to a carbon it’s chiral
2 non superimposable images can be created
These are a pair of enantiomers
priority sequencing of sp3 carbon atoms
lowest priority at the back(dashed line)
clockwise then R
anticlockwise then S
how to measure optical activity
specific rotation = observed angle of rotation/ pathlength (dm) x density (gcm-3)
what is a meso isomer
no optical rotation due to internal compensation these are in molecules with 2 identical chiral centres
what are diasterisomers
stereoisomers which are not enantiomers
whats the maximum number of stereoisomers that you can get in a molecule
2 to the power of n
where n is the number of chiral centres
what are confermers
inseparable isomers thst have different spacial arrangements as a result of free rotation about a single bond
what is the newman projection of molecules
front view of molecule
what are the types of conformer
ecliped conformer and staggered conformer
what type of conformer is more stabled
staggered conformers as they are 12kJmol-1 more stabled then eclipsed
what is tortional strain
the energy barrier to rotation
what is the origin of tortional strain
repulsion between electron clouds
what are the types of conformers when there is a priority group on each carbon
synperiplanar (ecliped with the priority groups in the same place), synclinal (staggered with both at similar place) , antiperiplanar (staggered priority groups opposite sides) , anticlinal ( eclipsed on opposite sides)
what is the energy levels of each orientationss
antiperiplanar, synclinal, anticlinal and synperiplanar (fronm lowest to highest)
what are atropisomers
enantiomers that result from restricted rotation around a simple bonds
what is a gauche conformation
where the angleis more then 0 degrees but less than 120 degrees
why is cyclopropane astrong electrophile
it can’t adopt a different conformation other then flat and is therefore high energy
why do some cyclo compounds adopt alternative shaped structures
to minimise tortional strain
what is the signifivcance of chair and boat
they are both formationsthat cyclohexane can tak to minimise tortional strain
what does boat conformation look like
little chem book reference
what does chair conformation look like
reference chem book
what is a level one functional group
one bond to a heteroatom from carbon
what are the level one functional groups
halogens, alcohols and thiols, ethers, thioethers, epoxide, peroxides, amines
what is an epoxide
a cyclic molecule with 2 carbons joined together that are also joined to the same oxygen
what is a peroxide
2 O bonded together with alkyles on ether side
what is a thiether
an ether but instead of an O its a S
what are the level 2 functional groups
multipul halogens, ketones, aldehydes, hydrates, hemiacetal, acetal, imine, oximine
what is a hydrate
a carbon with 2 alcohol groups
what is a hemiacetal
a carbon with one alc and one ether
what is an acetal
a carbon with 2 ethers
what is an imine
a secondary carbon with a double bonded nitrogen that has an r group
what is an oxime
a secondary carbon with double bonded nitrogen which is bonded to an alcohol
what are the level 3 functional groups
halogens, carboxylic acids, esters, anhydrides, acid chlorides, amide, nitrile
what are the level 4 functional groups
carbonate, carbamate, urea and isocyanate
what is a carbonate
a carbon bonded to a double bonded O with 2 ether groups
whats a carbamate
a carbon with double bonded O with 1 ether and 1 amine
what is urea
a carbon with a doubled bonded O and 2 amine groups
what is an isocynate
carbon with double bonded O and double bonded N
which functional level is most readily oxidised
4
what is oxidation
increase in functional group level
what is reduction
decrease in functional group level
what is an inductive effect
the way electronegative atoms polarize electron density in a single bond
what is heterolytic bond cleavage
the movement of 2 electrons to the more electronegatice atom
what is homolytic bond cleavage
the movement of one elctron to 2 different atoms from the single bond (shown with fish hook arrows) creates radicals
what is mesomeric effect
the movement of e- density froom either double bond or lone pair by resonance
what is hyperconjugation
alkyl groups will donate electrons to another carbon due to the partial overlap of empty carbocation orbital
reaction priority rules
e- flow must start from an electron rich site
move towards an electron poor site
the flow must end somewhere good (not have five bonds to a carbon and ideally at an electronegative atom)
charge is concerved (if there’s a negative charge at the start there must be at the end)
priority of electron rich sites starting point
negative charge
lone pair
double bond
single bond
where the starting point goes to
positive charge on carbon or H+
atom next to an otherwise positive ion
somewhere that leads to a positive charge
partially positive charge
what is a base
electrophile will react with a postve carbon or partially positive carbon
what is a nucleophile
acid a positive hydrogen or partially positive hydrogen will react with a base
