5 STRUCTURE & SHAPE OF ORGANIC MOLECULES Flashcards

1
Q

what exerts greater repulsive force? lone or bonding pairs?

A

lone pairs exert greater repulsive force

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2
Q

what are functional groups?

A

atom/group of atoms that have a specific structure/sequence. these groups convey certain physical/chemical properties for a molecule

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3
Q

what are hydrocarbons?

A

compounds containing only carbon and hydrogen

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4
Q

what are alkanes?

A

contains a single c bond. c-c

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5
Q

what are alkenes?

A

contains a double c bond. c=c

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6
Q

what are alkynes?

A

contains a triple c bond.

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7
Q

what are aromatic compounds?

A

ring with double/single c bonds.

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8
Q

what are alkyl/aryl halides?

A

halogen connected to alkane/aromatic compound

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9
Q

what are alcohol?

A

hydroxl group (OH) connected to carbon, etc. single bond w carbon

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10
Q

what ether?

A

oxygen and element connected to carbon, etc. single bond w carbon

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11
Q

what are amines?

A

nitrogen connected to carbon,etc. single bond w carbon

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12
Q

what are aldehydes?

A

oxygen double bonded to carbon. hydrogen bonded to same carbon

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13
Q

what are ketones?

A

oxygen double bonded to carbon.

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14
Q

what are carboxylic acids?

A

oxygen double bonded to carbon. hydroxyl connected to the same carbon.

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15
Q

what are esters?

A

oxygen double bonded to carbon. another oxygen single bonded to same carbon.

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16
Q

what are amides?

A

oxygen double bonded to carbon. nitrogen single bonded to same carbon

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17
Q

why are specific wavelengths of light absorbed by molecules?

A

because energy levels are quantized

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18
Q

what does IR absorption correspond to?

A

bond vibrations (specific molecular motions). IR energy is absorbed when frequency of light matches the “normal” frequency of vibrations for that bond

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19
Q

molecular bonds can be thought of as…?

A

balls and springs that vibrate as a harmonic oscillator

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20
Q

what is k in regard to the harmonic oscillator?

A

force constant that is proportional to strength (“stiffness” of the bond)

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21
Q

what is μ in regard to the harmonic oscillator.

A

is the reduced mass. a value that compensates for the two different masses in the bond (harmonic oscillator)

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22
Q

in the harmonic oscillator, what does a large k indicate?

A

a tighter spring aka STRONGER BOND! also larger k=higher energy vibrations

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23
Q

how does mass affect bonds?

A

lighter atoms = higher energy vibrations = stronger bonds

24
Q

what is the formula for alkanes?

A

Cn H(2+2)

25
Q

what can be said for larger molecules?

A

large = more surface area = more dispersion forces = higher boiling point

26
Q

what is constitutional isomerism?

A

same molecular formula but different connectivity/bonding sequence

27
Q

what are conformations?

A

quick? spatial arrangements resulting from rotations around single bonds. THEY ARE NOT ISOMERS!!!

28
Q

what has higher energy? eclipsed or staggered?

A

eclipsed conformations have higher energy due to repulsion

29
Q

what is steric repulsion?

A

if same atoms get too close to each other, more repulsion = higher energy = more unstable

30
Q

what is the formula for cycloalkanes?

A

CnH2n

31
Q

what can be said bout rotation with cycloalkanes?

A

rotation around c-c single bond is hindered

32
Q

what are cycloalkanes?

A

ring of carbon atoms connected by single carbon bonds

33
Q

what can be said bout rotation with

A

there is some c-c rotation, but restricted

34
Q

what are the types of cyclohexane conformers?

A

boat and chair

35
Q

how common are boat conformations? chair conformations?

A

the occurrence of boat conformers is less than 0.1%. the rest is chair conformers

36
Q

all the substituents in a chair conformer are…?

A

staggered

37
Q

what are axial substituents? for what type of conformer?

A

six substituents directed up and down. this is for the chair conformer of cyclohexanes

38
Q

what are equatorial substituents? for what conformer?

A

substituents are pointing laterally away from the ring’s center point. for the chair conformer of cyclohexanes

39
Q

what is flexing in regard to conformers? (flipflop)

A

axial substituents change to equatorial positions (vice versa)

40
Q

what is important to note about steric hindrance and conformers?

A

molecules tend to adopt most stable conformer - the conformation with least steric hindrance

41
Q

when is cis-trans stereoisomerism possible in cyclohexanes?

A

when two or more non-hydrogen substituents are on different carbon rings

42
Q

why do cis-trans isomers not convert at rotations?

A

because they are isomers and not conformers

43
Q

what does unsaturated mean?

A

the molecule doesnt contain the max # of possible hydrogen atoms. compounds with fewer than 2n+2H atoms are said to be unsaturated

44
Q

what is the formula for alkenes?

A

CnH2n

45
Q

what is the formula for alkynes?

A

CnH2n-2

46
Q

when can a double bond only have cis geometry? why?

A

in rings with 7 members or less, a double bond can only have cis geometry because the trans arrangement would be too strained

47
Q

what is the formula for max number of cis/trans isomers?

A

n being number of c=c bonds. 2^n. 2 to the power of n

48
Q

what is chirality?

A

type of stereoisomerism.

49
Q

what can be said about chiral objects?

A

chiral objects have no plane of symmetry and their mirror images are non superimposable.

50
Q

what can be said about achiral objects?

A

achiral (nonchiral) objects have a plane of symmetry and their mirror images are superimposable

51
Q

what are enantiomers?

A

same formula and bonding sequence. no plane of symmetry and non superimposable images

52
Q

two enantiomers have the same physical/chemical properties, except…

A

act/rotate on plane-polarized light differently.

react with other chiral molecules differently

53
Q

what are stereocenters?

A

aka chiral centers. atom in middle of diff substituents (no plane of symmetry)

54
Q

what are fischer projections?

A

representation of 3D structure of molecules with chiral carbons

55
Q

what about chirality in biomolecules? give example and state effects of its R form and S form. what can be learned from this example?

A

thalidomide.
r form: anti nausea effect for pregnant women.
s form: teratogen - causes birth defects.
chemicals can pass through placental barriers

56
Q

what rotates plane polarized light? (ppl)

A

optically active molecules are chiral and rotate ppl. achiral molecules can not.

enantiomers rotate ppl in opposite directions.

57
Q

how does +/- rotate molecules? is this related to R/S

A

+ to the right, - to the left. nope they are both independant