MCAT Organic Chemistry Flashcards
No resonance structures can be drawn for atoms that are truly __
sp3 hybridized,
What are the three main criteria of resonance stabilization?
- Resonance contributors in which octet rule is satisfied for all atoms are more important in resonance structures in which they are not
- Resonance contributors that minimize separation of charge (formal charge) are better than those with large separation of charge
- In structures with formal charges, more important for resonance contributor has negative charges on more electronegative atom and positive charge on less electronegative atom
A bronsted-lowry acid is a molecule that__
can donate a proton
Bronsted-lowry base is a molecule that __
accepts protons
The strength of the acid is determined by the ___
extent to which the negative charge on the conjugate base is stabilized
The more electronegative a substituent __
the more electron withdrawing it is, the more acidic the compound will be
___are species that have unshared pairs of electrons or pi bonds and are frequently negative (or partially negative) charge
Nucleophiles
___ are also lewis bases
Nucleophiles
What are the three trends of nucleophilicity?
- Nucleophilicity increases as negative charge increases
2. Nucleophilicity increases going down the periodic table within a particular group F OH-
___ is how easy it is for the electrons surrounding an atom to be distorted
Polarizability
___ are electron-deficient species
Electrophiles
__have a full or partial positive charge and frequently have incomplete octets
Electrophiles
___ is a measure of how strong an electrophile is
Electrophilicty
Electrophiles are also known as_
Lewis acids
___ attack ____
Nucleophiles attack electrophiles and donate a pair of electrons
Basicity decreases_____
down a family in the periodic table
__ arises when bond angles between ring atoms deviate from the ideal angle predicted by the hybridization of the atm
Ring strain
____ are compounds that have the same molecular formula but their atoms are connected together differently
Constitutional isomers
___are compounds that have the same molecular formula and atomic connectivity but differ about rotation of sigma bond,
Conformational isomers, they are the exact same molecule
A staggered confirmation is ___ than an eclipsed conformation
More stable
Why is the staggered conformation of a molecule more stable than the eclipsed conformation?
- More stable because of electronic repulsion, covalent bonds repel one another, in staggered confirmation the sigma bonds are far from each other
- Less steric hindrance
If the path traveled is clockwise, the absolute configuration is __
R (Clock-R-wise)
If the path traveled is counterclock wise the absolute configuration is___
S
In Fischer projection vertical lines are assumed to___
Horizontal lines are assumed to___
Vertical lines are assumed to go back into the page
Horizontal lines are assumed to come out of the page
compounds that are non-super imposable mirror images of each other
Enantiomers
What is the difference in properties of enantiomers?
Most enantiomers will have same chemical propertiesL
- Melting point
- boiling point
- polarity
- solubility
A compound that rotates plane-polarized light clockwise is said to be __
detrarotatory (d) or (+)
A compound that rotates plane-polarized light in the counterclockwise direction is said to be __
levorotatory (l) or (-)
What is the magnitude of rotation of plane-polarized light for any compound (specific rotation) dependent on?
- structure of molecule
- concentration of sample
- path length through which light must travel
An equal mixture of enantiomers (racemic micture) in solution will have a specific rotation of ___
0, it is not optically active
A D sugar means that on the highest chiral center in its fischer projection___
the hydroxyl group is on the RIGHT
All epimers are ___
Diastereomers, but not all diastereomers are epimers
Epimers that form as a result of ring closure are known as__
anomers
Cyclization of glucose occurs when_
C-5 hydroxyl group attacks the carbonyl carbon
When there’s an internal plane of symmetry in a molecule that contains chiral centers, the compound is a __
meso compound
___are diastereomers that differ in orientation of substituents around a ring or double bond
Geometric isomers
On a TLC plate, where would you find the most polar compound where would you find the least polar compound, why?
- Most polar component will interact more with the polar stationary phase, travels at slower rate
- Least polar component has greater affinity for the solvent than the stationary phase, and travels with the mobile solvent at faster rate to the top
In column chromatography, what is the order of flow into the collection tube?
The first polar compounds in Column (flash) chromatography will spend more time adsorbed to the polar solid phase and travel slowly down the column
-The compounds in Column chromatography can be expected to leave the column in order of polarity (least polar to most polar)
In High performance liquid chromatography, what is the order of elution?
The order of elution is REVERSED for HPLC,
The more polar compounds elute first, as they have high affinity for the mobile phase and the less polar compounds are slowed because of their interactions with the nonpolar stationary phase
What is the order of elution of size exclusion chromatography?
The large molecules travel out fastd because the path is more direct
The smaller particles have a more complicated path taken through (intrapaticle pathway) the porous polymeric beads
In gas chromatography, what is the order of elution?
The more voltaile components emerge from the column first and the less volatile components emerge from the column later
What properties of a compound are most important in gas chromatography?
The volatility or boiling point
Branching of hydrocarbons tends to have what effect on boiling and melting point?
Branching tends to inhibit van der Waals forces by reducing surface area available and reduce attractive forces
BRANCHING LOWERS MELTING POINT AND BOILING POINT
What state would you find: Small hydrocarbons (1-4 carbons) Intermediate hydrocarbons (5-16 carbons Large hydrocarbons (16+ Carbons) at room temperature
- Small hydrocarbons are gases at room temp
- intermediate hydrocarbons are liquids at room temp
- Large hydrocarbons are waxy solids at room temperature
___is the process of raising the temperature of a liquid until it can overcome the intermolecular forces that hold it together in the liquid phase, the vapor is then condensed back to the liquid phase and subsequently collected in another container
Distillation
All D-sugars have ___ configuration at the penultimate carbon atom because they are derived from D-glyceraldehyde
R configuration
All L-amino acids are __ configuration because they are derived from L-glyceraldehyde
S configuration
Which amino acid is the only amino acid with the R configuration because the R group has higher priority over the carboxylic acid group
Cystine is R-cysteine
Two important synthetic methods for the production of amino acids are __ and __
Strecker Synthesis and Gabrial Synthesis
___ utilizes ammonium and cyanide salts to transform aldehydes into a-amino acids
Strecker synthesis
___ is a general separation technique that can be used to separate amino acids based on their charge
Gel electrophoresis
On gel electrophoresis, a positively charged amino acid will migrate towards __
negative electrode
On gel electrophoresis, a negatively charged amino acid will migrate towards__
positive electrode
Peptide bond is just an ____ between two amino acids
Amide bond
What makes a peptide bond planar and rigid?
Resonance delocalization of the nitrogen’s electrons to the carbonyl oxygen. It gives substantial double bond character to the bond between the carbonyl carbon and the nitrogen.
NO ROTATION AROUND PEPTIDE BOND
a-helices of proteins are always __,___,and have __ amino acids per turn
a-helices are always:
- Right handed
- 5 angstroms in width
- 3.6 amino acid residues per turn
Proteins such as hormone receptors and ion channels are often found with ____ transmembrane regions integrated into the hydrophobic membrane of cells
a-helical
Phospholipids are derived from __
Diacylglycerol phosphate or DG-P
Phospholipids are ___, substances that efficiently solubiilize oils while remaining highly water-soluble.
Detergents, detergents are like soaps, but stronger
What effect does an increase in unsaturated fatty acids have on the melting point of the phospholipid bilayer?
It decreases the melting point and increases membrane fluidity
Cholesterol is considered a ___
polycyclic amphipath
Polycyclic means several rings, and amphipathic means displaying both hydrophilic and hydrophobic characteristics
Glucose is a __ sugar
Polyhydroxy aldehyde glucose aldohexose
Fructose is a___ sugar
Polyhydroxy ketone, or a ketohexose
Epimers are NEVER__
enantiomers
Six membered ring structures are termed __
Pyranoses
5 membered ring structures are termed ___
Furanoses
How does the ring structure of glucose form?
OH on C5 nucleophilically attacks the carbonyl carbon (C1) forming a hemiacetal
In beta glucose the anomeric hydroxyl group is pointed__
up (Be UP)
How do you draw a Haworth projection of sugars?
- ALL GROUPS on left of fischer notation are ABOVE the ring in haworth notation.
- If the sugar is a D-sugar CH2OH goes above the ring on the carbon to the left of the oxygen in the ring
- For an alpha sugar place the OH below the ring on the carbon to the right of the ring oxygen
The anomeric carbon in a ring structure is always numbered__
1 or 2
BH3 will selectively reduce carboxylic acids to __
primary alcohols
NaBH4 will selectively reduce Ketones to __
Secondary alcohols
In glucose the anomeric carbon is part of a ___ functional group
Hemiacetal
Bond-dissociation energy is related to ___
bond length
In the electron transport chanin Complex 4 adds __protons to the intermembrane space per oxygen-reducing reaction
2 protons
In the electron transport chain Complex 3 pumps __ protons across the intermembrane space
4 protons
An oxygen connected by single bonds to two carbon-based groups is an __
ether
__ involves nitrogen atom connected to two carbon atoms with a double bond
Imine
The affinity of a protein for its ligand is measured by its ____ which quantifies the tendency of the protein-ligand complex to degrade into protein and ligand
Dissociation constant Kd
*Small Kd indicated a LOW TENDENCY for the complex to break apart and indicates high affinity because only a small amount of a ligand is required to achieve a high amount of binding
In an electrolytic cell, the deposition of solids as a result of the reduction of a metal ion onto the cathode is known as __
electroplating
