carboxylic acids and carbonyls

Question 1

how does GC seperate compounds

Answer 1

by solubility in teh stationary phase

Question 2

compound B comes out of the GC befoer compound A ,what does this suggest ? (1)

Answer 2

compound B is more soluble in the gas/ mobile phase and less soluble in the liquid/ stationary phase

Question 3

when reducing an aledheyde to alchohol, what did i forget?

Answer 3

the extra H; eg CH2OH NOT CHOH

Question 4

Answer 4

Question 5

also, how many peaks would we see for each of these in a c NMR spectra?

Answer 5

FIRST react all with Tollens’ reagent AND silver mirror/ppt/solid (formed) with compound D

THEN react C and E with H2SO4/H+ AND K2Cr2O7/ Cr2O72–/Na2Cr2O7 AND colour change OR green colour with compound C

no change OR no reaction OR no green colour with compound E

C=5 PEAKS, D=5 E= 4 (because there are 2 ymettrical ch3’s on teh skeletal formula

Question 6

how would you find the number of C nmr peaks ?

Answer 6

count the carbon enivronments (symettrical environmetns count as one )

Question 7

draw the structures from the oznolysis of hexa 2,4 diene ?

Answer 7

Question 8

Instead of propane- triol , hwat should it be named?

Answer 8

propane 1,2,3 triol!!1

Question 9

apart from the alchoohol, draw the other strucutres that are present after ALKALINE hydrolysis

Answer 9

remember when adding sodium hydroxide, teh carboxylic acid end of each carboxylic acid turns into a sodium carboxylate salt!!

Question 10

suggest why goats milk can cause coronary heart disease

Answer 10

one of the fatty acids is trans which may increase / cause / produce (the level of) ‘bad’/LDL cholesterol

Question 11

how woudl you draw the skeletal formula of a carboxylic acid ?

Answer 11

Question 12

what would you witness when k2cr2o7 and sulfuric acid is added?

Answer 12

the colour changes from orange to green !

Question 13

why is said compound heated under reflux rather than distilled off?

Answer 13

to ensure carboxylic acid is formed (1)

Question 14

this compounds shows stereoisomerism.. draw the isomers of this compound

Answer 14

its optical isomerism… ( just reflect it.. )

Question 15

how would you calculate percentage yield ?

Answer 15

moles of desired product/ moles of reactants

* 100

Question 16

what is the MR of the compound that is proceeding to be revelealed?

the MR of this compound is 160

Answer 16

The mr of this compound is 174 not 176

why? because even though you add “16” from the one oxygen adde, remember , in carboxylic acids the COO group doesnt ahve any hydrogens therefore 2 hydrogens are taken out o the net addition is “14”

160 + 14 = 174

Question 17

Answer 17

Question 18

how would you assign the double bond here?

Answer 18

count from the lowest double bond ie- the oxygen double bond in the ester group .

Question 19

Question 20

what is the difference between a cis isomer and a trans isomer (1) ?

Answer 20

is isoemr has the lowest priority groups on the same side whereas trans isomers has them on opposite sides

Question 21

IMPORTANT NOTE FOR CHRIAL CENTRES

Answer 21

CONSIDER THE HYDROGENS

Question 22

how would you go about counting carbon atoms

Answer 22

Label each carbon with a number; and then coutn them1

Question 23

how many chiral centres are here ?

Answer 23

https: //www.youtube.com/watch?v=8RLo7e2Mne4&t=41s
6: 41

Question 24

suggest the advtange ( remember suggest questions need you to think outside the box) to develope a syntehtic route from a natural substawnce rather than making it from scratch

Answer 24

developing a snyhtetic route ensures correct chriality as only one optical isomer is formed

( if you were to make it from scratch, many differetn byproducts would form therefore different chiralities )

Question 25

NOTE, LOOK AT THE AMOUNT OF MARKS; EG 4 MARKS = 2 STEPS WITH EXPLANATION OF CONVERSIONS

Answer 25

how to do this question :

1. analyse functional groups etc .. list out the conversions needed.
2. DONT OVERTHINK IT! JUST STATE WHAT NEEDS TO BE ADDED (eg here i overthought the fact that the posititioning didnt seem right but that didnt matter)
3. just write out what needs to be done to convert between functional group

model answer here :

reagent: NABH4, aldehyde produces alchohol and conc H2SO4 for esterification of alchohol and aldheyde to produce an ester (THIS BOLD BIT IS IMPORTANT!)

Question 26

primary amine group

Answer 26

CO(NH)(CH3)

Question 27

2ND PAPER STARTS HERE

Question 28

define condensation polymerisation

Answer 28

when momoners join to form a polymer and small molecuel such as water or hcl is released

Question 29

NOTE:

state the obvious

Answer 29

eg if hydrogen bonds are mentioned…

then say

” hydrogen bonds for with water”

Question 30

not: why should we test drugs before distributing them

Answer 30

for side effects

Question 31

NOTE

Answer 31

to find the isomer of a ketone, just move the keton group 1 to the left/ right

Question 33

Question 34

ch3ch(ch3)ch2

how many carbon environments?

Answer 34

3 NOT 4

its 3 because the ch3 attached to one of the carbons count as one carbon environment, not 2

Question 35

why would it be hard to seperate two compounds from gas chromotography

Answer 35

similar RETENTION TMES ( REMEBER GAS CHROMTOGRAPHY: ALL ABOUT RETENTION TIMES)

Question 36

general structure of a triglyceride

Answer 36

Question 38

draw repeat unit for this ?

Answer 38

remember: its a repeant unit so its just ONE of the units NOT two !