chem 14c – Chemistry – Flashcards
Unlock all answers in this set
Unlock answersquestion
| Lactone |
answer
| an ester contain within a ring |
question
| bond angles |
answer
| sp3-109.5 |
question
| hybrid orbitals |
answer
| sp1 sp2 sp3 |
question
| geometry of hybridization |
answer
| sp3=tetrahedral sp2=bent sp1=linear |
question
| torsional strain |
answer
| e- repulsion when an atom passes by another atom/group by rotating -rotation is allowed as long as it does not significantly decrease orbital overlap.-in newman projection, it is motion of getting the molecules to line up |
question
| steric strain |
answer
| strain caused by e- repulsion on an atom/group by another near by atom or group. -in newman projection, it is when the substituents are line up |
question
| angle strain |
answer
| strain resulting from non ideal angles. |
question
| ring strain |
answer
| strain from being in a ring, combination of torsional and angle strain. |
question
| functional groups |
answer
| group of atoms that determine molecular properties ( chemical, physical, or biological) -allows use to make predictions about a molecule. -chemical rxn is influence by e- distribution and molecular structure. |
question
| gauche,stagger, ecilpse. |
answer
| gauche-biggest groups 60 degrees next to each other stagger- evenly spread out elcipse-overlap |
question
| planar |
answer
| -has equal bond angles -permit p orbital overlap=inc stability -max p orbital overlap occurrs when p orbitals are parallel(that is when they are planar)=max bond strength and max stability -conjugations have partial pi bonds (dotted lines in resonance hybrid) that restrict rotation and force planarity -if there is significant torsional strain, the molecule won't be planar. |
question
| axial vx equatorial |
answer
| axial up and down, equitorial=left/ right |
question
| Resonance: |
answer
| when a molecule can be represented in 2 or more valid lewis structure. - must have a pi orbital, except in rare case where sigma bond break for resonance. -allows electron delocalization -e- are delocalize and stablize by resonance -less e- repulsion the more stable the molecule. -chemical reaction often produce stable products ( resonance, conjugation, etc) |
question
| Resonance contributor |
answer
| one lewis structure that contributes to resonance -has no physical reality |
question
| resonance hybrid |
answer
| a weighted avg of resonance contributor. - single lewis dont strucutre that takes all of the resonance contributors into account. -look at this when considering any property (ie: bond length) instead of individual resonance contributor. -helpful way to locate conjugate atoms |
question
| patterns of resonance: |
answer
| 1. lone pair pi bond 2. open octet pi bond 3. pi bond lone pair and open octet 4. aromatic ring pi bond circulation ( rotation of pi bond in one ring at a time) |
question
| rules of resonance |
answer
| 1- most important- full octet 2. max # of covalent bond 3. least number of formal charge. 4. negative charge are best on the most electronegative atom and positive charge are better on the least electronegative ( -) 5. resonance is strong between elements in the same row. |
question
| barrier to rotation:47 |
answer
| -partial pi bond=higher barrier to rotation=planarity=stability |
question
| heat of formation(ΔHf) |
answer
| enthalpy change when a substance is made from an element in their standard state. the smaller the ΔHf means the more stable a molecule is. |
question
| catalytic hydrogenation |
answer
| -the adding of a hydrogen, disrupts conjugation ,but doesn't completely destroy it. -the lower the entalpy of hydrogenation the more stable the isomer is. |
question
| conjugation |
answer
| -the special stability provided by 3 or more adjacent, parallel, overlapping p orbitals -has partial pi bonds that restrict rotation and force planarity( result of conjugation) -increase stability -a planar conformation is required to achieve conjugation -require atoms to contribute a pi bond (sp and sp2 hybridization) -unlike resonance, conformation isomers are real structures with distinct lifetimes. |
question
| colors in conjugation |
answer
| more conjugated= more color(visible light) ΔE= HOMO/LUMO gap ( change in energy from ground state to excited state) -high HOMO/LUMO= uv light inc pi bond=dec. HOMO/LUMO gap=dec. in energy required to excite an electron -there is no relationship between the stability of a molecule and its color. stability is determined by the energy of the molecule and color is determine by the difference of energy between 2 molecular orbitals |
question
| partial pi bonds(dotted lines in resonance hybrid) |
answer
| -shorter than single bonds, longer than a carbon-carbon double bond -partial pi bond=higher barrier to rotation=planarity=stability -two adjacent sp2 atoms have a partial pi bond(or full) due to p orbital overlap -rotation of sigma bond and torsional strain decrease p orbital overlap destroying partial pi bond and dec. the stability |
question
| coplanar |
answer
| pg: 65 when torsional strain destabilization < conjugation stabilization=coplanar(dihedral angle of 0 degrees -is perpendicular if torsional strain destabilization> conjugation stabilization( ie. 2 methyl group repulsion) |
question
| aromaticity |
answer
| the extra stability possessed by a molecule that meets the following criteria: 1. cyclic/ ring structure 2.must have a p orbital 3. pz orbital must overlap and be planar(or close to it) 4. orbital arrangement must result in a lowering of energy: 4n+2 - prevented by torsional strain or steric strain b/c they interfer with p orbtial overlap -ring strain usually doesn't interfere with p orbital overlap... so doesn't prevent aromaticity. |
question
| diradical pg: 69 |
answer
| a species with two unpaired electron |
question
| hybridization: |
answer
| the presence of pi bonds is a result of hybridization not a pi bonds cause hybridization. |
question
| absolute configorations |
answer
| relative spatial postion of attachments at the sterocenter. assign r for clockwise and s for counter clockwise. |
question
| chiral |
answer
| -non superimposable mirror image -superimposible mirror image = achiral -allows optical activity |
question
| priority rule |
answer
| lowest priority and in the back for atoms with the lowest atomic number. lone pairs have no protons or nucleus so its priorit is always lowest. |
question
| diastereomer |
answer
| stereoisomer that is not an enantiomer |
question
| enantiomer |
answer
| one of a pair of stereoisomer that are non superimposable mirror images - only physical property of enantiomer is the direction the rotate plane-polarized light |
question
| meso compound |
answer
| achiral compound that contains two or more sterocenter |
question
| optically active |
answer
| -rotates plane-polarized light |
question
| stereocenter |
answer
| carbon atom with four different attachments -2^n stereocenters at most? |
question
| stereoisomer |
answer
| -same molecular formula,but different orientations a. conformational b.geometrical isomer(14b) c. optical isomers-two types: diastereomers and enantiomer) one of a set of isomer of identical constitution(sequence of atomic attachments) but differing in the arrangement of their atoms and non interconvertible by rotation around a single bond |
question
| biological effect |
answer
| -when a compound interacts with an enzyme or receptor in the body -enzyme and receptors are constructed by proteins and have very specific shape and size |
question
| constitutional isomer |
answer
| same molecular formula, but different connectivity |
question
| conformational isomers |
answer
| different rotation around a single bond -has a physical reality, unlike resonance |
question
| aldose |
answer
question
| amylopectins |
answer
question
| amylose |
answer
question
| anomeric carbon |
answer
question
| disaccharide |
answer
question
| fisher projection |
answer
question
| furanose |
answer
question
| glycoside |
answer
question
| haworth projection |
answer
question
| hemiacetal |
answer
question
| hexose |
answer
question
| ketose |
answer
question
| pentose |
answer
question
| polysaccharide |
answer
question
| pyranose |
answer
question
| saccharide |
answer
question
| tetrose |
answer
question
| triose |
answer
question
| α and β and D configuration |
answer
| -refers to the stereochemistry at the anomeric carbon d= means the carbohydrate has the most common natural configuration -alpha is easier to break down than beta α if when the CH2OH and OR groups are trans in the α anomer. -β when CH2oh and anomeric group are cis in the β anomer |
