Block 1 Flashcards
1
when a line structure has nothing on the end of the line (eg. Terminating out to space) what is there
The start of the line is a carbon with invisible H attached
What is the rule for the visibility of H in line structure
Hs bonded to Carbons are invisible but if they are bonded to Hetero atoms, their bond to the hetero atom must be visible and the Hydrogen visible
in line structure, if the line terminates at a hetero atom this only represents
a bond from the carbon to the hetero atom (C–Z) not a bond to another C and then Z (C–CZ)
What is an ether and how to do you name it
R-O-R’. The way to name it is by identifying the parent chain first attached to the O and then and then the other chain. Put them in alphabetical order or say ‘di alkyl’ if its the same alkyl group and then have ether at the end.
What is an acid anhydride and how to do you name it
R- C=OOC=O -R’. So like a symmetrical carboxylic acid (without the H in middle). The way to to name it is to name the two Rs attached to the functional group and then put them in order alkanoic alkanoic anhydride.
What is a nitrile (cyanide) and how to do you name it
C=_ N. It is named by alkane nitrile
How do you name secondary and tertiary amines
Parent chain is identified with it called alkyl amine. The other groups coming off the N is listed before as the locant. (eg. N-methyl-N-ethyl or N,N-diethyl
What is a thiol and how to do you name it
C- SH (a sulfur group). It is named by alkane thiol.
How do you name an acid halide
alkanoyl halide
What does the primary, secondary and tertiary classification mean?
The functional group is bonded to a carbon that is bonded to 1 carbon (1’), 2 carbons (2’) or 3 carbons (3’)
When you draw an sp bonds what is a key thing to remember for line structure
The bond angle is 180 , its linear so it is a flat line
Compare and contrast pi and sigma bonds
The first bond is a sigma bond. It is made from s orbitals which are spherical. They overlap straight on, therefore they are stronger than pi bonds which are the side on overlap of p orbitals that look like roundbottom hourglasses.
What orbitals does Carbon have and what are the different types of hybridisation
Carbon has 2 s orbitals and 2 p orbitals.
It can be sp3 hybridised where the 2s orbital mixes with all three p orbitals, sp2 hybridised where one p orbital doesn’t mix and sp hybridised where 2 p orbitals don’t’ mix
What is the geometry, bond angles and number of groups attached for sp3 carbons
4 groups attached to carbon in tetrahedral arrangement, bond angles 109.5
What is the geometry, bond angles and number of groups attached for sp2 carbons
3 groups attached to carbon in trigonal planar arrangement bond angles 120
What is the geometry, bond angles and number of groups attached for sp carbons
2 groups attached to the carbon in linear arrangement bond angles 180
What are constitutional isomers
compounds with the same molecular formula but have different atom to atom bonding sequence
What type of molecular formular of C and H would tell us it is fully saturated
Cn H2n +2
If the molecular formula is CnH2n what would it tell us about the compound
It has one double bond or one ring
What is a conformational isomer
molecule with the same molecular formula, same atom to atom bonding sequence but the arrangement in space differs–> interconverting by rotation around a single bond (no bond breaking)
What are the two ways of drawing conformers
Sawhorse and Newman projection
What is the most stable conformer
Anti - where the repulsion are minimised by the largest groups attached to the 2 central carbons are staggered and opposite
What is the least stable conformer
Syn - where the largest groups are eclipsed
What is the other staggered conformer called and what is its arrangement
Gauche- where the largest groups are not the greatest distance apart
by how much does a conformational isomer bond turn to get to the next conformer
60 degrees
Which conformer is more stable : boat or chair and why
Chair is more stable because all bonds are staggered whereas in the boat conformer, all bonds are eclipsing
On converting from Chair A to Chair B (ring flip) what happens regarding up and down and ax and eq groups
All axial groups become equatorial and vice versa but- whats up stays up and whats down stays down
What is the favoured chair conformer for substituted cyclohexanes
One that has the largest atoms/groups in the equatorial position- largest group means number of bonds sticking out rather than than the atom size
define configurational isomers and
Same molecular formula, same atom -atom bonding sequence but the arrange in space different. Interconversion only by breaking and reforming covalent bond
When is use of cis and trans to describe configurational isomers used
When describing the relative positions of substituents on the same (cis) or different (trans) sides of the ring in cyclic compounds
What is the condition for E/Z isomers to exist
There cannot be two of the same groups bonded to the same carbon in the double bond of the alkene
What is Z configuration
The high priority groups are on the same side of the double bond
What is E configuration
The high priority groups are on opposite side of the double bond
What is condition for enantiomers
there has to be sp3 carbon with 4 different groups attached (has a stereogenic centre) and it has a chiral carbon. Therefore it is non superimposable on its mirror image
What does achiral mean
The sp3 carbon has two identical groups attached therefore there is a plane of symmetry and the molecue is superimposable
What is the experimental observation of enantiomers
They have the same physical and spectroscopic properties but in plan polarised light, it is optically active, and one enantiomer will cause clockwise rotation of light (+) and one will cause anticlockwise rotation of light (-).
What is the overall rotation of a racemic mixture of enantiomers
zero as both will rotate equal amounts of light in both directions
What type of notation is the stereochemistry of the enantiomer denoted by and how do you find it.
R/S notation. First you rank all groups from highest (1) to lowest priority (4) . Orient the molecule so the (4) is facing away from the page. Then the direction of counting 1 to 3 (decreasing priority) determines the orientation. R is clockwise and S is anticlockwise.
what are diastereomers
configurational isomers that do not have a mirror image relationship
what is the name for octane groups attached to something
stemane
What are alroxy substituents
R group with a bond to O. Eg. Methoxy for CH3O
What do you name an propyl group attached at the second carbon as a substituent
isopropyl or 2-propyl
When naming a molecule with a C=C/ triple bond and a functional group containing oxygen how do you do it
Identify the parent chain based on the O functional group. Then replace the ‘a’ of the alkane stem with -#-e saying the position of the C multiple bond
Define electronegativity
the ability of a bonded atom to attract electrons to itself
Which is more polar: double or single bonds and why
double bonds are more polar because the pi electrons are more mobile than sigma electrons.
What are momentary dipole dipole interactions and how are they increased
The dominant interaction between molecules where the assymetric distribution of electrons of a molecule causing temporary dipoles to form. This can induce temp dipoles in neighbouring molecules and lead to interactions of electrostatic attractions.
Force increases with molecule size
What is dipole-dipole interactions and how are they increased
Due to the polar bonds in a molecule, permanent dipoles are formed. Strength increases with overall polarity of the molecule. This includes the individual polarity of bonds and the shape of the molecule.
What is H bonding
special case of dipole-dipole interactions of molecules including O-H, N-H and F-H which are very polar. The positive dipole of H interacts strongly with the negative dipole of the electronegative atom.
When comparing boiling point what do you have to think about
- Size of the molecule-> (increasing size increases strength of temp dipole -dipole) and
- The molecular shape (strength increases when the branching is decreased because Intermolecular forces are stronger in closer proximity)
- Presence of polar bonds–> for compounds of similar molecular weight, more polar groups = more dipoledipole interactions.
* however for different molecular weights, the temp forces will have the greatest effect on Bp.
What is the factor that determines solubility
The overall polarity of a molecule -> the size of the hydrocarbon chain and the polar groups used.
Describe how chromatography works
The mixture of interest is absorbed on a polar statioary phase. An even more polar mobile phase (solvent) is passed over the stationary phase, moving the components of the mixture along. The mixture then separates into different components where the more polar solutes don’t move as quickly as they are attracted to the stationary phase whereas non polar ones move quite quickly
What does a double headed curly arrow mean
2 electrons are moving from the tail to the head
What does a single headed curly arrow mean
1 electron is moving from the tail to head
What is two ways that a covalent bond can be broken and the names
Symmetrically => homolytic bond cleavage so the 2 single headed arrows and neutral species with 1 unpaired electron (radicals).
Assymmetrically => heterolytic bond cleavage so one double headed arrow moving 2 electrons from the bond to the more electronegative atom in the bond resulting in ionic products.
How is free radical notated
it has a flat dot next to it
What does a polar reaction involve
One electron rich partner donating an electron pair (nucleophile) from their lone pairs or pi electrons to the electron acceptor ‘electrophile’ (neutral or positively charged)
What is the reaction type that breaks 1 sigma bond and forms one sigma bond
substitution
What is the reaction type that breaks 1 pi bond and forms 2 sigma bonds
addition
What is the reaction type that breaks 2 sigma bonds and forms 1 new pi bond
elimination
What are the two mechanisms of nucleophilic substitution
Sn1 => step wise bond breaking and then forming
Sn2=> bond breaking and forming at the same time (one step)
State the steps for the Sn1 mechanism
Heterolytic bond breaking forming a carbocation intermediate followed by polar bond formation with nucleophile attack. Then in order to give a neutral product there is a heterolytic bond breaking
