EK Ch2 Org Chem Flashcards

Question

ketone

Answer 1

same molecular formula but different bond to bond connectivity, i.e. different connections between atoms ex. isobutane (C4H10) and n-butane (C4H10)

Answer 2

same molecular formula but different compounds

Answer 3

not true isomers, confomers are different sptial orientations of the same molecule - at room temperature atoms rotate around their sigma bonds, resulting in a mix of conformational isomers at any given moment ( think newman projections)

Answer 4

- staggered is lower energy than eclipsed confomers exist at higher energy - difference in energy levels is due in large part to steric strain - simplest way to distinguish btw confomers

Answer 5

two unique molecules with the same molecular fomrula and same bond to bond connectivity ex. enantiomers and diastereomers

Answer 6

= nonsuperimposable mirror images of one another, they have the same molecular formula and connectivity, but are not the same moelcule becuase they differ in configuration ex mirror images of each other, must have hte opposite absolute configurations at each and every chiral carbon - they have opposite absolute configurations at all of their chiral centers, if a molecule has more than one!

Answer 7

any carbon is chiral when it is bonded to 4 different substituents!

Answer 8

COUNTER CLOCKWISE

Answer 9

* compounds may be compoudns without a chiral cetner or molecules with internal mirror planes * for comoounds without an enantiomer, or for an equal mxiture of enatiomers, there are so many millions of molecules colliding with photons that on average, photons leve the compound with the same electric field orientation with which they went in * since no single molecular orientation is favored, the net result is no rotation of the plane of the electromagnetic field

Answer 10

1. interactions with other chiral compounds 2. interactions with polarized light

Answer 11

* same molecular formula, bond to bodn connectivity but NOT mirror images of each other * not the same compound * differ in their boiling points, melting points, solubilities, rotation of plane polarized light * so these pairs have different physical properties (above) and in their chemcal properties

Answer 12

* max number is 2ⁿ * n= the number of chiral centers * so this formula is what the max number ofopticlaly active stereoisomers ( so dia. and enati.) that a single compound have is related to teh numebr of its chiral centers followed by this formula

Answer 13

multiple chiral centers, optically inactive plane of symmetry through their center which divides hte moelcule into two halves that are mirror images of each other - because of their symmetry the chiral centers offset each other and theoverall compound does not rotate plane-polarized light ACHIRAL\*

Answer 14

BIOCHEM ## Footnote diasteromers that differ in configuration at only one chiral carbon

Answer 15

cyclic diasteremers that are formed whne a ring closure occurs at an epimeric carbon, chiral carbon of the anomer is called the anomeric carbon carbohydrates classified according to their configuration at the anoemric carbon!

Answer 16

differnt physical proeprties! * cis have dipole moment, trans do not * because they have dipole moment, cis molecules have stronger intermolecular forces than trans molecules, leading to higher boiling points--\> it takes more energy to make them boil since they're "stuck" together by stronger intermolecular forces * sicne substituents concentrated on the same side cis molecules do not form crstyals as readily, and therefore have lower melting points than their respective trans isomers\*

Answer 17

* rate determing step is formation of carbocation, is the SLOW STEP * so rate dependent on only one of the reactants * this step has nothing to do with nuc, so rate is indepdent of hte concentration of the nucelophile and is directly proportional to teh concentration of the substrate, substrate is the electrophile or the molecule being attacked by nuc * LG simply breaks away on its own leaving a carbocation behind * second step happens very quickly, nuc attacks carbocation * ONLY IF starts chiral c, both enantiomers are produced * intrermediate carbocation is planar and the nucleophile is able to attack it from either side

Answer 18

* rate is dependent on concentration of nuc and the substrate * attack from behind * rate dec from primary to secondary, third whould stericlaly hinder * do not occur with tertiary carbons/substrates! * if nuc a strong base and the substrate is too hindered an elimination E2 reaction may occur, in which case nuc acts as a base taking a proton and halogen leaves the susbtrate froming a cc double bond * bulky nucleophiles also hinder sn2

Answer 19

* unimportant sn1, important sn2 * if nuc beahves as a base, elimination will occur so use a less bulky nuc, a neative cahrge and polarizaibility add to nucelophilicity! * electronegativity reduces nuc * nuc decreases going up and to the right on the periodic table! * base is always a strong nucelophile than its conjguate acid, but nuclepholicity and basicity are not the same thing!

Answer 20

* stabilize nuc and any carbocation that may form * that can hydrogen bond! * stable nuc slows sn2 reactions, while stable carbocation inc the rate of sn1 reactions, so polar protic solvents inc the rate of sn1 and dec he rate fo sn2

Answer 21

* cannot form a hydrogen bond * do not form strong bonds with ions and thus increase the rate of SN2 reactions while inhibiting sn1 reactions * in sn1 solvent is often heated to reflux. boil, in order to provide energy for the formation of carbocation * solvolysis hte solvent acts as the nuc

Answer 22

A chiral molecule is one that is asymmetrical in a way that makes it non-superimposable on its own mirror image. Often, this asymmetry results from a carbon atom, or chiral carbon, that is attached to four different substituents. Chiral molecules promote the rotation of plane-polarized light. In contrast, achiral molecules are superimposable and do not rotate plane-polarized light. In the specific context of amino acids, a chiral amino acid must have four different substituents bound to its α-carbon. This means that the α-carbon is a chiral center, or stereocenter. (A chiral amino acid might also have other stereocenters – in fact, threonine and isoleucine both do – but the α-carbon is the likely focus of an MCAT question.) Of the 20 standard amino acids, 19 are chiral. \*\*\*Only one is achiral: glycine, which contains two identical hydrogen atoms attached to its α-carbon. This means that glycine is unique in that it does not rotate plane-polarized light. Additionally, glycine is the only standard amino acid that cannot exist in two enantiomeric forms. (Enantiomers are mirror-image stereoisomers that rotate plane-polarized light in exact opposite directions.)

Answer 23

Of the 20 standard amino acids, 19 are chiral. Only one is achiral: glycine, which contains two identical hydrogen atoms attached to its α-carbon. This means that glycine is unique in that it does not rotate plane-polarized light. Additionally, glycine is the only standard amino acid that cannot exist in two enantiomeric forms. (Enantiomers are mirror-image stereoisomers that rotate plane-polarized light in exact opposite directions.) In chiral amino acids, the configuration of substituents around the α-carbon can be described in multiple ways. Under the R/S system, which is typically most familiar, all chiral amino acids are S except cysteine, which is R. Alternatively, amino acids (as well as sugars) can be classified using the D/L system, which classifies molecules based on their resemblance to glyceraldehyde. The MCAT is unlikely to ask you to determine whether an amino acid is D or L based on its drawn structure alone. However, it is important to know that only L amino acids are used by eukaryotic cells. (You can remember “L” for “living” eukaryotic cells.) However, prokaryotic – or bacterial – cells do use select D amino acids for incorporation into their cell walls.

Answer 24

Amines (R–NH2, R–NHR’, or R-NR’R”), imines (R=NH or R=NR’), and enamines (C=C–NH2, C=C–NHR, or C=C–NRR’) are nitrogen-containing compounds with medium melting/boiling points that can act as weak bases. Sulfur-containing functional groups contain the root “thio” and generally act similarly to the corresponding oxygen-containing groups.

Answer 25

sulfonate ester