Organic Chemistry Flashcards
True or false, the longer the chain length, the higher the boiling point, melting point, and density.
True
True or false, the more branching a carbon chain has, the higher the boiling point, melting point, and density.
False
What does meso mean?
That a molecule with two chiral centers has a plane of symmetry in it. Also, that molecule is superimposable.
What are diastereomers?
Types of stereoisomer that are superimposable.
What are enantiomers?
Stereoisomers that are superimposable.
A single bond has a ____ bond length and a ____ bond energy than a double or triple bond.
Longer, Lower
In the cyclohexane boat configuration, where are substituents preferred to be?
In the equatorial position.
Are meso compounds optically active?
No
What are racemic mixtures?
Mixtures with an even number of R and S chiral centers. There is no optical activity.
Conformational isomers are associated with Newman projections, true or false?
True.
Describe the initiation, propagation, and termination steps in free radical halogenation.
- Initiation: Heat is applied to a diatomic halogen forming two free radical halogens.
- Propagation: One of the free radicals pulls a Hydrogen off an alkane while the other reactions with the carbon forming RX.
- Termination: Two free radicals react and form a diatomic halogen.
Which carbocations are the most stable? Which free radicals are the most stable?
Tertiary carbocations and Tertiary free radicals (•CR3)
Name the five Electrophilic aromatic substitution reactions.
Halogenation Sulfonation Nitration Alkylation Acylation
What’re vicinal and geminal diols?
Vicinal diols are two alcohols on two separate carbons. Geminal means two alcohols on the same carbon.
E1
Unimolecular, 2 step, elimination reactions where the rate is dependent upon the substrate. The LG is eliminated forming a carbocation and a Beta proton is removed by a base to form an alkene. Requires polar solvents, good leaving groups, and favors high temperatures.
E2
Bimolecular, 1 step, elimination reactions where the rate is dependent upon the substrate and the base. The Base removes a beta proton that is antiperiplanar to the halogen while the halogen is removed simultaneously. The more substituted alkene is preferred.
SN1
Unimolecular, 2 step, nucleophilic substitution reaction where the rate is dependent upon the substrate. This is favored in protic solvent, it gives racemic products, and prefers more substituted electrophiles.
SN2
Bimolecular, 1 step, nucleophilic substitution reaction where the rate is dependent upon the substrate and the nucleophile. A strong nucleotide attacks the molecule from the backside releasing the LG and inverting the stereochemistry. This favors aprotic solvents and unhindered molecules.
What is the general formula for the amount of carbons and hydrogens on an alkane chain, alkene chain, and alkyne chain?
Alkane = C(n) H(2n+2)
Alkene = C(n) H(2n)
Alkyne = C(n) H(2n-2)
where n is the number of Carbon atoms.
What is the formula for the degree of unsaturation?
Number of double bonds = 1/2 (2n+2-m) where n is the number of carbons and m is number of hydrogens.
What factors determine a good nucleophile?
- Charge-the more negative, the better.
- Electronegativity-In protic solvents, the the more electronegative the nucleophile, the worse. In aprotic, the more electronegative, the better.
- Sterics-the more bulky a nucleophile, the slower the rate of reaction.
Do EWG or EDG’s make something more acidic? Why?
EWG make a molecule more acidic because it increases the range of electron delocalization.
What are ortho/para activators, ortho/para deactivators, and meta deactivators?
o/p activators are EDG such as -OCH3, -OH, and -NH2 that increase the rate of reaction.
o/p deactivators are EWG halogens that decrease the rate of reaction.
meta deactivators are EWG such as -NO2, -COOH, and -CN that also decrease the rate of reaction.
What factors determine a good leaving group?
Weak bases (or conjugate bases) such as H20, HSO4, Br, Cl, I, and the conjugate base of tosic acid.
In mass spec, what does the tallest peak indicate?
The tallest peak is the base peak indicating the most common ion.
In mass spec, what is the M+ peak?
It’s the molecular ion peak, which is the peak with the highest mass/charge ratio.
In NMR, deshielding occurs upfield or downfield?
Downfield (to the left)
In NMR, what is the correlation of the number of peaks to the number of adjacent hydrogens?
n + 1 = peaks, where n is the number of adjacent hydrogens.
What is the IR spec frequency of a carbonyl group, an ether, an alcohol, an alkane, an alkyne, an Alkene, and an amine?
Carbonyl= 1700 Alcohol =3300 (broad) Ether=1100 Alkyne=2200, and 3300 Alkane=2900 Alkene =3100 Amine= 3100-3500 (sharp) Aldehyde= 2800
What are epimers?
Compounds that have the same optical activity but only differ at one carbon.
What are anomers?
When the newly formed chiral center differs between 2 of the same cyclic compounds. Alpha is when the OH group is down and beta is when it points up.
What’s mutarotation?
When there is a change in anomers, such as from alpha to beta.
What is the bond called between two monosaccharides? Water is a product.
Glycosidic bond
How is cellulose linked? What about starch and glycogen?
Cellulose is linked via 1,4 beta glycosidic linkages while starch and glycogen are linked via 1,6 alpha glycosidic linkages.
In alpha helix structures, where do they hydrogen bonds exist?
Between a carbonyl oxygen and a amine nitrogen 4 residues away. An example is keratin.
On beta sheets, where are the hydrogen bonds?
Between the carbonyl oxygen and an amine nitrogen on different rows.
What’s the difference between fibrous and globular proteins?
Fibrous proteins, such as collagen, are long strands or sheets. Globular proteins, such as myoglobin, are spherical in shape.
